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