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