I use Ethernet over powerline to stream my Slingbox back to my wireless AP. Unfortunately most new Roku models don't have an Ethernet port.
The easiest solution is to purchase a wireless range extender. It will work out of the box with only a few simple options to set up. Available for both G & N networks.
Another solution is to use a wireless router/ AP and set it up as a repeater bridge. If you can live with using G you can flash an old router with DD-WRT and then set it up. (IMHO I get stronger signals using G vs N ).
If you look on e-Bay you can find Linksys 54G routers flashed with DD-WRT for $30 - $50. I set a 54G up last week and it does take some time and experimentation even with good instructions. I had to change settings on both my primary router, access point and repeater bridge. If you aren't experienced tweaking router setting this probably isn't going to be a good option for you.
Roku still makes boxes with Ethernet. Hopefully will continue to do so too.
If you check second hand stores it's easy to find Linksys 54G routers. I have a pile of them that I might get rid of now that I wired my House. Anyways you need to find Linksys 54Gs that are hackable: http://en.wikipedia.org/wiki/Linksys_WR ... _revisions
and power plugs: http://www.monoprice.com/products/produ ... 1&format=2
Usually DD-WRT or Tomato (many community supported versions: http://linksysinfo.org/index.php?forums ... rmware.33/
) is the way to go.
Also going to like a Dollar Store and picking up poster paper, glue stick & foil will allow you to make Wifi boosters that work really well: http://youtu.be/sUTT8wdN_VA
Also once hacked raise transmit power to 70mw: http://lifehacker.com/344765/turn-your- ... ith-tomato
Monoprices routers also offer a good number of features too: http://www.monoprice.com/products/subde ... 21#1052102
However if you can wired will always be more reliable than wireless which is convenient.