Even though De Rossi has no experience in European competitions, I am sure he can handle the pressure. De Rossi has managed to make Roma better and of course it will be a good morale to face Brighton. Brighton is at the same level if we look at the performance of the two teams in each league. But AS Roma is more favored because they have experience at European level but I think Brighton can give a surprise in that match. I predict the match will end in a draw.
In fact, AS Roma game has changed since De Rossi's presence, but De Rossi abilities still need time to proof and to ensure his strategy will help provide a win in all match conditions. IMO, De Rossi needs to ensure in this match, is how his team can anticipated the fast tempo from EPL clubs. If De Rossi is successful, then it is possible that AS Roma can win the match vs Brighton. Playing in their home based can help AS Roma playing with their good confidence.