The cylinder on my Riso RP3700 will not engage because it is hitting the lower roller.

SOURCE: Paper feeding problems Riso TR1510

first try paper feed clutch.. make sure nothing is blocking paper path...

SOURCE: my Riso RP 3100 is not getting ink to the drum

Ok,if you strip the drum open and remove the drum body there is a gear with a one way bearing on the inking roller remove that gear and clean the bearing and the sarft it is running on.If the machine is giving the same problem that ger needs to be replaced.
Remember if you strip the drum the drum is full of ink and can get everything full of ink.If you dont know how to strip the drum it is beter to get a qualified technicin to do the job.
Hope this was helpfull

SOURCE: Paper feeding problems Riso TR1510

refix your ink cartrdige also check there is not any paepr jam issue.
also some times printer neeed servicing creates this type of issue.

SOURCE: Riso RP 3700 indicates that the master is still on

It honestly sounds like the unit is going to need some repair work. All the types of troubleshooting possible have been done by the looks of it. It's a hardware problem which is impossible to repair remotely.

You can call Riso at 978-777-7377 to find the nearest service center.

Sorry about that.

Thanks for your patience and understanding,

Tim

SOURCE: i have a problem withz riso rp 3105 ep

Many people have an problem. Some people have a solution.
To provide a solution you have to describe your problem!(Simple, but the hard truth. Must I be sorry for the clear words?)