I've changed cams several times keeping the same rockers without issue. The theory behind using new rockers is the wear pattern. More aggressive cams hit the pads at differing angles than a stocker and vice versa. The resulting wear on the pads is mostly on the leading edge of the pad and possibly a different pad curvature than another cam's wear.
Other considerations are the transfer and retention of particles from cams with different alloys and. or hardness. The latter came from a metallurgist I had a lengthy conversation with years ago. Those scenarios would be on a microscopic level and most likely not cause any issues. Though anything IS possible.
If you want to reduce the chance of failure have the pads polished perpendicular to the cam scrape on the pads. Shop can do that on the crank polishing belt or you can do it at home with wet 600 grit cloth/paper. Don't use a hard flat surface if you do this yourself, you don't want to disrupt the curvature of the pads.
replace any rockers with deep grooves or scratches either way.
