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