If I'm using a PS3 to stream Netflix in one room of the house is it possible to stream at the same time in another area of the house using a Roku, provided I have a second streaming discs? This is using a wireless router BTW.

As far as I know, yes, although depending on the speed of your internet connection, the quality may well go down, possibly significantly.

That said, where I was seeing 2 and 3 dots worth of quality a few months back, I now regularly get 3 and 4 dots, with 4 more often. They're improving their algorithm, I think, 'cause my internet access ain't getting any faster.

Like Ken said - you should be able to do it, but doing it SIMULTANEOUSLY could degrade the bandwidth to the point that it becomes annoying.

This probably doesn't apply in your situation (with PS3 and Roku) but I know that you can only link your netflix account with one xbox360 at a time.