No you cannot unlock a network lock by rooting. They are two different things.
1) Mobile country code (locked to a country’s mobile network)
2) Mobile network code (locked to a mobile phone provider’s network)
3) Mobile station identification number (SIM lock to a specific phone)
Most common is a mobile network code used by AT&T to lock iPhones users to their AT&T network. And mobile station identification number used by Verizon – to lock user of WCDMA/CDMA phones to their network. In this case the SIM card is enclosed in the phone so you don’t have access to it.
Rooting an android phone is a different animal altogether. Rooting gives you administrative user level access to the software of the android phone. It is similar to jailbreaking on Apple iDevices.
With administrative user access to your android phone you can…
1) delete applications that have been installed on your phone by your network provider that you don’t want to use (usually adware/bloatware/trialware).
2) back up your phone operating software including all the applications that you have installed to your SD card (usually xRecovery or Titanium Backup)
3) install custom ROMs specifically designed to run on your android phone – for example Cyanogen 2.3 Gingerbread ROM for Xperia X8.
4) use applications that require root access, for example tethering applications to create wifi hotspot using your phone’s 3G network so you can surf the internet with your laptop.