I've built several of Meng Qi's Rollz5+ units for folks and for myself. They are great.
I'm happy to build one for you if you want, but I will say that it's a fairly basic project in the grand scheme of SDIY, and worth doing yourself if you're a bit savvy. Happy to answer any questions about the build.
As for comparisons with the Plumbutter, I haven't had the pleasure of playing one but I would imagine that the PB2 has much more going on in the variety category while the Rollz focuses in on more detail on the "drums" part of the PB2. The Rollz5+ has 2 each of the following: 3-rolls, 4-rolls, 5-rolls, and 6-rolls. It has 2 AV Dogs, 2 Ultrasounds, and 2 Gongues (like on the PB) which are the "sound making" parts of the unit.
The PB2 on the other hand only has a 3-roll and a 4-roll, but it has much more in other categories, like a deerhorn, snare, man with red steam, and lots of cv/knob control.