From what I've read about the Roku, the PQ isn't even 720p. I'd have one if it did at least that. I just spent a couple hours last week reading the reviews about the Roku and I was disappointed. Might well buy a cheap Sammy BD player just to stream NetFlix. Not that much more expensive and it does everything. I've seen the Sammy 1500 for about $179. That little bit of money is worth it for better PQ. And I'm not a Sammy fan. I've got a great Sony BD player, but it doesn't stream NetFlix. Neither do the Pannys.
You need to check the date on any Roku reviews you read - 720P is a relatively recent addition and Dolby Digital 5.1 was just added yesterday via a software update. I don't think there's any streaming Netflix content with DD5.1 as of yet.
Also, if Netflix is only providing 720P streams, the Sammy BD player will only provide better PQ is it has good upscaler.