Note that some of the newer RadioRA stuff has an IR interface built in. I recall at least wall controllers. I believe there are others as well. As mentioned above, you can also use the RA-IR.

I just set up a RA-IR with a MX-900 in my theater a couple days ago. The combination works well. I like how you can set a macro such that the lights turn on at preset dimness when you hit pause on the remote, and one such that the lights turn off when you hit play. The RA-IR controls consistently work, but they seem to have a different speed of turning on/off than standard RadioRA. Also note that the Lutron controls for the RA-IR in the MX-900 database of my software were very messed up. Each control would trigger two actions. For example selecting light 7, would cause the RA-IR to set both 2 and 7. I had to learn codes from my Harmony remote to get the correct IR codes. This may relate to using older software on my MX-900. I am having trouble getting the new version, due to their restrictive software policies.