As a teacher I can see how Rollyo can be great for students. If they are doing a report on Texas history, I can pick and choose what sites they are able to search. So instead of students searching in Google for George Bush and getting hundreds opinion pages, they will get factual information instead. Check out the Rollyo I made for Famous Texans research.
On the down side it can limit their results and get them to have very similar papers. There may be some site that I forget to include on the Rollyo search that would have really helped. Overall the idea of Rollyo is great for teachers to get their students to keep their eyes on their work. However, I firmly believe that students still need to be "let loose" on search engines such as Google so they can learn how to properly evaluate their sources when they go home and search on their own.