Roberts designs are very popular, just like bad sex.
I think about one or maybe two out of 10 ever made (and there are several THOUSAND out there, according to Roberts...although I bet most of those are still in the backyard) sail up to the designer's expectations. When done right, they are tough, go anywhere boats, but to do them right, they need to be assembled from CNC-cut kits (and assembled by skilled welders), or built by REALLY skilled welders who are also machinists.
I've stepped aboard a few now, and seen one worth even taking for a sail test. The rest were ill-finished, lop-sided, indifferently welded or insufficiently zinc/tar coated to pass muster even in the Great Lakes.
If you find a good one, you'll be lucky. I think they are out there, but rare.