Welcome aboard. You'll fit on a Roadster no problem. Of course the pre-Roadster (ie 2009 and earlier) models had better peg position but get highway pegs and you do have more options for foot placement. Totally with you on the screen thing. Some people have fitted bat wing fairings but they completely spoil the look of the bike. Screens will annoy the crap out of you with the wind noise and buffetting and the headlights, gauges and tank on a Rocket do deflect quite a bit of the direct wind anyway. I know plenty disagree with me but I prefer to ride as nature intended (and not make my bike look stupid).
And yes, highly recommend a rider's backrest.