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