轮到你了=it's your turn. 该你了=it's time for you.

该=应该 该你了=应该轮到你来了 该你了is abbreviation

I might be wrong, but I think of 该你了 when it's sb's turn to do a chore (i.e. they should do it, from 应该), but you might be more likely to say 轮到你了 when playing a board game or cards, signing KTV etc. (i.e. the sequence has come around to you - 轮 mean wheel, which might help to remember).

该你了means it is time for y should or need to sth 轮到你了means there have order in time it is turn for y

“轮到 ”means “it is your turn ” “该 ” usually means “need”