Dove Manufacturing, Harland Sharp, and Rocker Arm Specialists all make roller rockers for the Y.  PRW was in the development stage but haven’t heard anything as of late on them.  Here are some links to past discussions of the some of the various aftermarket rocker arms.  Using the search function will bring up some other posts.

http://www.y-blocksforever.com/forums/Topic35870-3-1.aspx

http://www.y-blocksforever.com/forums/Topic29107-3-1.aspx

http://www.y-blocksforever.com/forums/Topic18985-3-1.aspx

http://www.y-blocksforever.com/forums/Topic8794-3-1.aspx

http://www.y-blocksforever.com/forums/Topic41429-6-1.aspx

http://www.y-blocksforever.com/forums/Topic37245-3-2.aspx