Hi.
I have one of those luggage tray things that goes in place of the passenger seat in my loft somewhere - never used it. TBH I could not really see the point of the tray when you can bungee tailpacks or drysacks onto the passenger seat just as easily and retain the option to bung a person on there instead as well

. But in theory the load would sit slightly lower, and plenty seem to like the look with it fitted.
I bought my bike with the pannier side-rails and a Givi rack and Top-box fitted (always avoided top-boxes till I got one by default - I soon got past the BOF looks once I realised how convenient & handy it is). My gf likes it as a back-rest and provides her with a feeling of greater safety as well, so it gets used quite a lot (I just don't put too much weight in it as its the wrong place for the handling).
I do have the BMW side boxes as well after picking a set up used - but before I got those I used a Hein Gericke roll-top dry-bag on the rear seat (cheap, weatherproof and simple), and Oxford Lifetime soft pannier set for trips which worked well too. I've also used an Oxford tailpack which was ok as long as you didn't want to carry too much, as well as various tankbags.
A small flyscreen that looks good is in short supply for the Rockster, but I do know of a couple....
Riceburner above has one solution (and definitely the cheapest!), but if you want to buy one rather than make something then a US Company makes the 'Laminar Lip' for the Rockster (
http://www.laminarlip.com/rockster.php) which is not too pricey, well-made and looks good fitted. I have one in the shed which I used for a while, but once I fitted higher GS handlebars I changed it for something a bit bigger (currently another US-made screen, a more universal type National Cycles Street Shield, modified with an additional adjustable spoiler).
There also some MRA 'Vario' universal type screens with handlebar mounting kits (
http://www.bikehps.com/acatalog/Screens ... Bikes.html) that look and work ok on the Rockster (I've one of those too - the VTNB one) - like a lot of screens they aren't exactly cheap though.