I think the XS has an RF remote which doesn't require direct line-of-sight. For other types that use an IR remote, the company claims the signal will bounce off the wall behind the unit and communicate that way. I didn't note any complaints about reception in the reviews so I'll take their word for it.
Roku's 2 XS (called the game remote) remote use Bluetooth technology to transmit signals, but all current units can (using iOS or Android apps) receives commands over the network (WiFi or Wired depending on unit and your connection). Here is the listing of current units --> http://www.roku.com/roku-products
That's correct, no line of sight is needed. The directions insert shows the signal bouncing off the ceiling or wall - and I guess that's what happens because I just point the remote slightly toward to ceiling and it works like a charm.