We have a 98 RC Twin with the 6 cyl. engine. We did a nearly 10,000 mile trip from Maine to Calif. criss crossing the Rockies twice with no issues BUT...you need to know you will not go up mtns at 65 mph and on some of the steepest passes it will be more like 25-30 mph. That was not a problem for us, we just took it easy and downshifted as needed. Practice the downshifting before you hit the mtns. It is a little tricky, pull shift lever down one gear without depressing the button on the gear shift. DO NOT use the cruise control going up or down the mtns. as this adds strain on the engine.
Many recommend adding a transmission cooler if you will be doing the mtns. regularly. Also change the transmission fluid and filter every 10-20,000 miles. If yours has more miles than this and you do not know if it was changed, do it before you leave on a trip.
Our Rialta did great, but we do treat it with respect as we really want it to last.