I have been messing about with various lashups for running locos on a rolling road but finally got around to making a proper one that was easily adjustable to fit various wheel arrangements and spacings. I was going to buy a kit from Model Engineers laser but then decided that I could make one myself easily enough.
The frame is just two 1 metre lengths of 20 x 20 aluminium X shaped extrusion screwed down to a length of wood by a bracket at each end. At the moment the spacing is set for 2½" Gauge but it could be set to suit other gauges.
The wheel supports are just pieces of 6mm aluminium bar drilled and tapped to hold two S625ZZ (20mm dia. x 5mm wide x 5mm bore) stainless steel bearings. I got these from AliExpress as they were really cheap. The supports themselves are bolted to the extrusions using the Tee nuts made for the job.
Lengths of 20 x 15 aluminium angle are bolted to the top of the extrusions to support the front bogies and the tenders. There's no need for those wheels to rotate.
The bolts are 5mm flanged button head stainless bolts of suitable length.
It works very well but it is noisy when the wheels are rotating. I could have done with making the front angles to support the front bogie a bit longer but I can always change them if necessary.