Really odd he'd be using Rockerverb guitar heads and not the Thunderverb heads that also have overdrive and clean channels but are designed as bass or guitar heads....and also have tube reverb. Similar to Rockerverbs but they have lower frequency response for bass use. Maybe he prefers that you can swap the power tubes on the Rockerverb and use either 6L6s, KT88s over 6550s? You can also use either KT88s or 6550s in the Thunderverb but no 6L6s, but it has a contour knob for the mids on the OD channel ad HUGE trannys...clean channel is the same as the Rockerverb.
I use the Thunderverb for grind on my 8- and 12-string bass octaves and an AD200B for the root notes/bottom.