Will Renesas V850ES/Jx3-E support 1 wire protocol (max detect temp/humid sensor)?
When it mentions that in the RHT03 Datasheet it's really just pointing out their protocol is different (Maxim/Dallas is more well known) so if you go searching you'll probably find Maxim 1-wire drivers. But it should interface OK with appropriate code, it just needs a general purpose I/O line. From the datasheet the voltage range is 3.3 - 6 V so either a 3.3 or 5 V microcontroller / supply will be OK.

I've noticed that on the Sparkfun product page for that device they have some sample code available. The code is written in C and for a AT89S52 microcontroller but that should give you a good starting point. The main things will be to work out how to do the equivalent I/O pin control and timing delays for your Renesas device.