It's not 100% correct expression but you can say "you are couch potato!" Couch potato can be 90% correspond with that expression. 뒹굴뒹굴 is more like mimetic word. When you are just sitting on the sofa or bed, and doing nothing... this action can be described "뒹굴뒹굴" but if you say 뒹굴뒹굴했어!! it would be a verb, which refer to the action what you are just sitting and doing nothing. Actually 뒹굴뒹굴 means the action "Toss-and-turn" on the bed...

뒹굴뒹굴 is a mimetic word.. when you are doing nothing but just stay in your room... you lay down.. and rolling yourself.. this side and that side... that's '뒹굴뒹굴' ex) 나 어제 집에서 그냥 뒹굴뒹굴 했어 ... means.. i stayed home and doing nothing but..rolling my self