http://shop.roku.com/Roku-Digital-Video-Player-Options-W5.aspx
Note: Only the high-end HD-XR model has been announced to support 1080p at this time, according to the forum post above.
From Roku forum site:
Model SD: $59 (was $79) (standard def)
Model HD: $69 (was $99) (720p)
Model XR: $99 (was $129) (1080p, WiFi N 2x2 dual band, USB)
In addition, we are announcing today that the XR will be software upgraded to support 1080p (currently its only 720p).