The Dual Rectifier Roadster is more like the DR Road King's little brother. I'm sure it'll get a pretty good DR tone, but from what I understand ALOT of the DR's tone comes from the DR cabinet. Without that massive cab, it's not going to sound exactly like a DR, but it'll get close
The combo forms of the basic DR were the Trem-o-Verb (no longer produced
AFAIK) and the Rect-o-Verb.