New to the forum, but not to the 250 tire on a Roadstar. You can run a 250mm tire in the stock swingarm as long as you are willing to modify several components.
First you have to detab the swingarm, remove all belt shield and brake stay supports. You need to obtain your HD rim and bearing set up (1" axle) and then grab a Softail 70 tooth 20mm pulley and a HD brake rotor as well as a rear brake caliper and support for a hardtail '84-99. The inner face of the mounting area of the pulley will have to be machined to allow the inner edge of the belt to run approximately 3/16" of the outermost edge of the 250 tire. I suggest you hold off doing that until you space the wheel in the swingarm.
Secondly you need to obtain BMS's front sprocket offset adaptor for your year of Roadstar, you will need to make special sized axle spacers to give you a centered rim, which should allow between 1/8"- 3/16" clearance of the rightside tire edge to the rightside of the swingarm. in doing this you will have 2 spacers on the right side of the axle, one between the bearing and the caliper carrier, and the carrier and the swingarm, leftside you will require 1 spacer between the swingarm and the leftside bearing.
Thirdly you need to purchase a 128 tooth 1 1/8" Falcon BDL carbonfibre belt and be prepared to rip it lengthwise down to 20mm on a band saw with use of a guide and some courage. It's not as tough as it sounds, I have done two... one that has 10,000 miles on it and a backup just incase!
Forthly is your fender, I run a fixed fender to swingarm setup, only a single up bobber. No passengers or bags with this setup. With some planning you could run a widened floating fender but it will have to stop short of the swingarms when the suspension travel is at its furthest point, since there is no clearance for the fender to pass between the swingarm and tire.