Can used Roller Lifters be installed on a new camshaft?

YES. "Roller" lifters are the only ones that can be re-used. This design lifter has a wheel (supported by needle bearings) attached to the bottom of it. The lobe the roller lifter rides on does not have any taper. This is a very low friction design and does not require the lifter to mate to the cam. As long as the wheel shows no wear, and the needle bearings are in good condition, the "hydraulic roller" or "mechanical roller" lifter can be re-used.