As you are rooted: Wireless network data are stored in
data/misc/wifi/wpa_supplicant.conf -- so you could basically copy all its
network entries from one device and insert them on the other. The entries look like
An easier way would be using the App Wlan Backup & Recovery (root): Backup all entries on one device, and restore them on the other. As you can see in below screenshot, the tool can even send the backup by mail -- so transfer to the other device should be easy:
But reading the comments on this app suggests it does not always work as expected: Users even recommend to use the manual way I described above.
Another option is using Titanium Backup, and restore the Wifi data on the other device. I did that successfully a couple of times, also cross-device and cross-ROM.
Third option is offered by the app Wifi Passwords (about USD 1), which allows you to share networks.