Do you mean they need separating into Pantone spot colours for actual spot colour printing? What is the nature of these images? Logos?
Without seeing them I can't be sure, but to be honest I suspect that unless you can get hold of vector versions, redrawing in Illustrator will be the only proper solution.
Often the case is that the original creator has vector versions, but the client has requested JPGs because they're familiar with that format and can open it on their computer. That one simple mistake must account for millions of labour hours in this industry.