Here is the full list of all 35 Disc Room achievements.
EXPLORE ALL ???? ROOMS
SURVIVE 20 SECONDS IN EVERY ROOM
HOLD DOWN FFW FOR 10 SECONDS STRAIGHT
DEFEAT THE ULTIMATE GATEKEEPER USING EVERY ABILITY
COMPLETE HARD MODE
UNCOVER THE GOLDEN MYSTERY
EXPLORE ALL ROOMS
SURVIVE 20 SECONDS IN EVERY ROOM IN ONE ZONE
FOLLOW THE PATH
QUIT TO MAIN MENU WITHIN 2 SECONDS AFTER DYING
SURVIVE 10 SECONDS IN EVERY HARD ROOM
EXPLORE ALL HARD ROOMS
SURVIVE 20 SECONDS IN ANY HARD ROOM
START HARD MODE
DIE FROM ALL DISCS
DISCOVER THE FOURTH GOLDEN ROOM
DEFEAT THE ULTIMATE GATEKEEPER
UNLOCK ALL 6 ABILITIES
DISCOVER THE THIRD GOLDEN ROOM
???? THE ????
FACE THE GOLDEN CARCASS
DEFEAT THE CARNIVOROUS GATEKEEPER
DEFEAT AND REVIVE AN ANTIBODY
WALK 10K STEPS
FEED ???? 4 ????
DISCOVER THE SECOND GOLDEN ROOM
DEFEAT THE PHANTOM GATEKEEPER
DIE FROM 4 DIFFERENT DISCS IN ONE LIFE
SURVIVE 60 SECONDS IN ANY ROOM
DISCOVER THE FIRST GOLDEN ROOM
SURVIVE 0 SECONDS OR LESS
DEFEAT THE OVERGROWN GATEKEEPER
END A RUN FROM THE MAP
DIE FROM ALL DISCS IN ONE ZONE
DEFEAT THE ARMORED GATEKEEPER