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