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