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