Here is the full list of all 20 Oh...Sir! The Hollywood Roast achievements worth 1,000 gamerscore.
Finish at least 65 scenes online
Finish at least 25 scenes online
Finish the basic tutorial
Have 6 characters receive 15 Golden Parrots each
Prove victorious in a battle royale of CFOs
Finish the career as The Greasy Wizard
Receive 69 Golden Parrots in total
Finish the career as Wisecrack
Have 3 characters receive 15 Golden Parrots each
Finish the career as Marilyn Nomore
Win a Roast in less than 3:40 minutes
Receive 15 Golden Parrots with one character
Finish the career as Chop Sue E.
Win a Roast losing less than half of your HP
Use a 55 points hot burn playing as a Single Star
Finish the career as Dirty Potter
Take 30 Pride points off your opponent with a single insult as a Single Star
Win a Cliffhanger
Use 3 Comebacks in one single player fight.
Win your first argument