An issue you will have to deal with is keeping the camshaft from walking forward when you switch to a roller cam. While adding a thrust button in the camshaft sprocket will do this you may want to use a timing chain that is machined for and comes with a roller thrust bearing. This bearing goes between the sprocket and block. In years past the block had to be machined for this but this is available as a bolt in set up now days. The thrust button is still used in this set up.
The reason this must be done is that a flat tappet cam pulls the cam rearward slightly due to the taper on the nose of the cam lobes. The same thing that makes the lifters spin. The roller cam does no have this feature.