This requires you to not only be rooted, but to also have Xposed installed. If you don't know what either of those are, this app will not work on your phone.
This app can be used to disable your proximity sensor along with other sensors on your device.
The proximity sensor is a sensor in most phones that tells the phone when the phone is near another object (generally a face.)
If your screen frequently goes black when on a phone call and you can't use it until the other party hangs up, this should fix your problem.
1: Can disable and modify most sensors on your phone (without requiring a restart).
2: Can use Tasker to control sensor statuses. (Pro Version)
3: Can use a blacklist/whitelist in order to decide which apps should use or ignore sensor settings you've set. (Pro Version)
If you have already purchased the Tasker In-App Purchase, you have the Pro Version already (and therefore the new blacklist/whitelist support.)
If you have issues, check the support thread @ http://forum.xda-developers.com/xposed/modules/mod-disable-proximity-t2798887/post53766106 or send me an email and we can work through your problem.