Soldering RoHS components with Pb-Sn solder
You don't need to make any process changes, as most RoHS components are plated with 100% matte tin, which is compatible with PbSn.

I've only heard of problems when mixing RoHS and non-RoHS for very fine-pitch, leadless packages as the stresses they can generate (leaded components have a little give) are much less tolerant of any undesirable intermetallics, and especially BGAs as they bring their own solder (balls) to the party (though hand soldering BGAs is extremely dubious at best.)

Assuming you've been using leaded solder with non-RoHS components before, keep the temperature the same, the matte tin coating needs negligible additional heat relative to everything else to dissolve into the tin-lead solder.