The usual role of the VP candidate is to play attack dog. I think Ryan will be well suited for this role. I expect Romney will try and stay above the fray and act presidential. Time will tell.
You think Ryan will defend naked Rumneys socialist agenda? Defend Rumneys liberalism? If he does then he is not a conservative in any sense of the word. And if he really is a conservative then he is in a real tight pigeon hole as the Veep. Rumney and his staff will do their best to keep a tight rein on him and his conservatism.