He said no such thing that I can see from this article as far as "dissing" Reagan or the agenda. He made a comment about how it was killed by 2006 and 2008 elections and now it is time for a new era to begin. Granted, I would have preferred he said something along the lines that it is time to reignite that same agenda and success, but what he did say wasn't "dissing" anything that Reagan did.
In the interview, Ryan says he is a member of GenX and he believes that this "new crop of people" and "new generation of people" coming to Congress are "firmly committed" to "founding principles" and "core principles".
I'd say Reagan was firmly committed to founding principles and core principles, and did all he could to advance the conservative agenda for the better part of 30 years. In fact, Reagan is still influencing American politics today. OTOH, Paul Ryan has done nothing to advance the conservative agenda. Hopefully that will change soon.
Unlike Boehner's first lieutenant Eric Cantor, I like Paul Ryan, but he should choose his words more wisely.