It may run for a while, but roller cams are ground completely differntly from flat tappet cams. The acceleation ramps are different, and less aggressive in the flat tappet cams. All he's basically done is to reduce some rolling friction.

However, flat tappet cams are ground with a slight side-to side taper to cause the lifters to rotate to minimize wear. That won't happen with roller lifters, because they're locked in place. I suspect that only a small part of lifter touches the cam, which can't be good in the long run.