How can I find obb folder in a rooted device to copy a game's sd data files and play game?
Here is a backup tool by Koushik Dutta (aka Koush) : Helium Backup

Using this you can backup complete app including data and restore it back. Just backup on your device, copy the files to your other device and restore it back.

I've tested it personally and it works flawlessly on non rooted devices.

Try this and let me know if you face any issues.