Here is an Android 4.2.2 Jelly Bean rooted firmware for the Rikomagic RKM MK802IV MiniPC.

This firmware is based on Rikomagic's stock firmware which seems to be designed for newer MK802IV models with updated WiFI/BT chip (AP6210 ?) The label on Rikomagic website for the firmware is: 

"MK802IV FW(130719):S/N from 201307**** till now"

Firmware Build information:

Kernel: Linux version 3.0.36+ (hotack@adminroot-X9DRL-3F-iF) (gcc version 4.6.x-google 20120106 (prerelease) (GCC) ) #46 SMP PREEMPT Wed Jun 19 17:36:33 CST 2013

Android 4.2.2 JB: rk31sdk/rk31sdk/rk31sdk:4.2.2/JDQ39/eng.hotack.20130619.182852:eng/opinions-on-teclast-p90hdst-keys

Custom firmware features:

• root with latest SuperSU version 1.41 (free version)
• removed most Chinese and unnecessary applications
• Google Play Store fixes so more application are visible/compatible
• updated busybox v1.21.0.git (2012-11-29)
• Unix like init.d boot scripts support, more details on init.d scripts here
• changed permissions on external sdcard to allow write access
• increased storage space for applications (/data partition) to 3 GB

Download: kasty-rkm_mk802iv-422-20130719_rooted3.zip

Please flash with Rockchip Batch Tool 1.7, use Restore button.

Please report any problem with this firmware, I can't verify this custom firmware works as I don't have a MK802IV device to test the custom firmware.