You will probably find that normal black-and-white paper (which can be handled under a safelight, unlike RA4) processed in any standard paper-developer produces better paper-negs than RA4 processed in film-developer. Having said that of course, I think that I recall Rodinal was originally (more than a century ago) also recommended for silver-chloride papers at a dilution something like 1+3.
Presumably you are completely unable to use any materials other than RA4 paper and Rodinal? If that is the case then a stronger mix of Rodinal, and a higher temperature, should increase the contrast - but it will most likely still look poor in comparison to normal materials. Out of curiosity, what are you planning to contact-print the negatives on?
Often the contrast 'problem' with paper negs, using b+w materials, is that it is too high. If you can find a fixed-grade, black-and-white, resin-coated paper for the negative then the contrast will likely be better (ie. lower) than using a multi-contrast paper, but they will work too. Pre-flashing the paper is also an option.