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