Success! If you want to use Tasker to enable something that requires root, you need to invoke the task through the "Secure Settings" (henceforth SS) plugin, rather than just setting thetask up by clicking GPS on. I had Secure Settings installed, but wasn't invoking it in Tasker.
A couple of other free apps are required to enable SS to do this, so I'll walk you through the process.
1) download 2 free aps from the Play Store: SS and "Busybox".
2) install BusyBox & give it SU rights
3) open the SS ap. If you have root, a message will come up telling you that to use the features that need root you must click on the "Helper" tab. Do it.
4) This will prompt you to install Helper. Do it.
5) Now you're ready to set things up in Tasker. Create a task and name it "GPS off" or "GPS on"
6) Click "+" and you'll get a long list of "Action Categories". For anything that requires root, you click "Plugin" and again on "Secure Settings".
7) Next to Configuration, click "Edit", and if you scroll down to the Helper Actions you can click on GPS , set it to turn on or off, and click save,
8) click the green checkmarks all the way back out, and make sure the green "On" is showing in the bottom right corner, and you should be golden.
Note that any task needs to be associated with a profile you've created as well. I've been testing with a simple one that turns on GPS when I open Maps. Next I'll work on how to set up a profile to recognize my work & home wifi networks and turn off the GPS when I'm there. But the GPS switching portion, at least, is worked out.