Here is the full list of all 21 Roy Cluse: Itsy-Bitsy Edition achievements.
Collect 50 martinis.
Avoid death with the bloodbag 10 times in one playthrough.
Die from brambles 25 times.
Collect all Roy Cluse skins.
Collect 100 gems in one playthrough.
Die from falling 25 times.
Feast on 50 other spiders.
Use your dash attack and land in brambles.
Die from flytraps 15 times.
Jump 200 times.
Collect 50 blood bags.
Travel an accumulated 10,000 feet.
Collect 50 bottlecaps.
Unlock Ash skin.
Unlock Blue skin.
Unlock Bubblegum skin.
Unlock Duke skin.
Unlock Green Machine skin.
Unlock Mrs. Roy Cluse skin.
Unlock Purple Boi skin.
Unlock Will of the Ancients skin.