Below is an list for all of the known secrets in the Rosenkreuzstilette series.
Rosenkreuzstilette/~Grollschwert~[]
Collecting the Black Forest's Treasure[]
Go to Trauare's stage, the Heiligtum des Wasserteufels. At the "fork-in-the-road" area after the Hydra mini-boss, drop down the hole in the floor. After safely falling through the vertical corridor without touching any of the spikes, you will come across the Black Forest's Treasure. Collect it, and from that point on, you can use Lilli to attack enemies.
Note that since you cannot return to a stage that has already been completed, defeating Trauare without collecting the treasure first will prevent you from using Lilli throughout the rest of the game.
Secret Room #1[]
Go to Sichte's stage, Zuverburg. At the room after the Bomb Turtle mini-boss, do not take the ladder. Instead, look for an opening on the right side of the room. Slide through that opening, and you'll be in a room with a Cross Tank, a 1-UP, and two Ball Bats. After you're done, you can use the ladder and head left to get back on the path to Sichte herself.
Secret Room #2[]
In Zeppelin Stage 4, when you get to the end of the area in the upper path where you view lots of bats flying in the background, use Silberflügel "Eins" (or use your wall climbing ability if you're Grolla) and climb up to the top of the wall at the right side. There will be an opening at the top that, once you head through, will lead you to a room heavily inspired by Bomberman games. Here, you'll find a Living Cross, two Octopi, six small Energy Pellets, six small Weapon Pellets, a Cross Tank, and a 1-UP. You can use Zornesbombe to clear the area of the bricks there, Bomberman style. Also note that there is a status bar based on that in the Vs. Modes of the Bomberman games, with four "player" stocks at 0 and a timer, after which if the timer runs out and you don't leave the room in time, you'll lose a life.
Secret Room #3[]
In the Final Stage, after being dropped off by Talos, head downward and find a good spot, and then use Silberflügel "Eins" a couple of times until you reach the top of one pillar (the fourth from the right). Stand at the left cliff of that pillar, and use Silberflügel "Zwei". Should Zwei have enough energy, you should be able to eventually reach a platform with a Cross Tank and a 1-UP.
Secret Room #4[]
This secret room is also in the Final Stage as well. From where Talos dropped you off, jump down the hole and free-fall until you land on a platform. Jump to another platform and use Silberflügel "Zwei". It'll carry you over to a platform with three large Energy Pellets, four large Weapon Pellets, and a 1-UP. When you feel like you're ready for the final showdown, you can jump onto the platform at the end and ride it over to the central platform, then ride the platform left of it back up to where Talos dropped you off.
Easy Mode[]
A feature exclusive to the officially translated version of Rosenkreuzstilette. If a player enters in the Konami Code on the [erka:es] logo screen: Up Up Down Down Left Right Left Right Attack Jump. When in effect this code causes bosses to take double damage. The player cannot save replays however and their time on the results screen will be recorded as zero. This can be used in ~Grollshwert~ mode but the player will have to manually exit back to the logo screen and enter the second code separate.
God Mode[]
A feature exclusive to the officially translated version of Rosenkreuzstilette, this code is given to the player as a reward for beating ~Grollshwert~. If the player enters Up Down Attack Jump on the [erka:es] logo screen they will unlock the games debug tools. F6 turns on and off God Mode which makes the player invincible to all forms of damage including spikes, lava, and crushing traps. Attempting to fall into a pit will have the player launched out of the pit as well. In addition God Mode dramatically increases the player's running, jumping and sliding speeds and distances. F7 gives the player full health and maximum lives. F8 kills the player and sets their lives to zero causing an instant Game Over.
~Freudenstachel~/~Weißsilber~[]
Collecting the Black Forest's Treasure[]
In Liebea's stage, the White Wasteland, after reaching the first area with blinding blizzards the player will pass a very large downwards snow drift. If the player descends in this drift and goes to the left they will find a hidden room with the Black Forest's Treasure. This will allow Freudia to use Strudel who behaves just like Lilli in the first game. When playing as Pamela there will be a Cross Tank there instead.
Just like the first game if Liebea is defeated before this item is collected the player is locked out of collecting it.
Secret Cross Tank[]
In the same room in Liebea's stage the path to the Black Forest's Treasure can be found, if the player uses Strudel's Frügel to fly to the upper right corner of the room they will find a hidden platform they would otherwise not see with a Cross Tank.
Secret Room #1[]
In Schwer-Muta's stage, the Zeppy Ruins, if the player has Strudel's Frügel they can use it on the fake warp zone pipe to the left of the start of the level to get on top of the structure in that room. If they then go even farther left they will find a free 1-up. Pamela cannot get up there however.
Secret Room #2[]
Shortly after descending from the Super Mario Bros. parody into the main part of the stage, if the player holds left they will pass through a fake wall to a room with a Cross Tank.
Secret Room #3[]
Later on in the Zeppy Ruins there will be a screen with three Skull Tanks there's a hidden room to the side by sliding through the right wall with a second Cross Tank. This also can be used as a short cut to skip the Needle section of the stage.
Friender Skip[]
In the Zeppy Ruins if the player ignores Zeppy's trivia question and instead goes down the middle path but immediately holds right they will enter the wall and can then slide through all three Friender rooms skipping them entirely.
Secret Room #4[]
Finally after the player has fought the three Frienders in the Zeppy Ruins they will go down one screen, if the player hugs the right wall and presses down they will descend a hidden ladder and can reach a room full of 100 coins to collect. This however requires Strudel's Frügel if playing as Freudia.
Secret Room #5[]
In Trauare's stage Heiligtum des Wasserteufels if the player takes the right path at the fork they'll eventually come up to a room with a few Lava Lotuses and a line of Needles moving up and down. At the far left of this room is a thin blue wall that is covering up blocks that can be destroyed with Frostfackel, beyond this wall is an area with a Cross Tank and a 1-Up.
Secret Room #6[]
At the very end of Iris Stage II if the player takes the top path just before the boss door and if they're observant they'll notice a translucent ladder when they approach the wall near the boss door. If this ladder is climbed it leads to a room with a Cross Tank and a 1-Up.
Secret Room #7[]
In Iris Stage IV the player can find another hidden ladder on the first screen by using Strudel's Hund on the top most platform and holding left. At the top of this platform is a Cross Tank, if the player then uses Strudel's Frügel to go to the other side of the room they will find a second ladder, at the top of this platform is a Max-Up if playing as Freudia or a Max-Down if playing as Pamela .
Level Select[]
Starting in Version 1.03 if the player selects "Exit" on the main menu and hits Select, not Start, a menu will open up allowing the player to select any of the Schwarzkreuz or Iris Palace II levels at their leisure. This was likely a debug feature left in the game as a mercy shortcut for newcomers, as indicated by it being it listed in the game's official site.