We've had our TerraTrike Rovers for about 6 weeks now and are still loving them.  But we have each rolled over a couple of times.  The Rover has the highest seat of any production trike I am aware of.  That makes it easier for old and/or overweight people to get on and off, and, for that I am grateful.  The result of having three wheels and a high center of gravity is that initial stability is great and final stability is non-existent.  Especially if you ride on uneven terrain, the Rover will go over quickly.  My first tumble was actually in my driveway. It has a bit of a compound grade at the entrance.  That spill broke my mirror and totally surprised me.  My last one was yesterday at the north end of the Katy Trail.  My own fault.  I tried to circle around faster than I should have.  So, how about it, you trike-engineers? Is there any sort of mod (to the trike, not my behavior) that will reduce the Rover's tipability?  I've looked the frame over pretty carefully and nothing jumps out at me.  I figured if anyone would know, it's this crowd.  BTW, I've been reading about 24 and 26 inch rear wheel upgrades to the Rover.   Seems like this would raise the seat even a fraction higher and make the problem worse. Anyone know?  Before anyone tells me that the fix is to trade the Rover in on a more high-performance trike, we are not ready for that solution yet.  We have some weight loss and conditioning commitments that we will meet before that is a consideration.  Thanks for any tips (no pun intended.)

To help keep the center of gravity lower, don't use a trunk (rack) bag on the top of a rear rack.  Use bags that hang either on the side of your rack or bags that hang on your seat. There are several reviewed on BentRider Online, one of which is Smokey Mountain Saddle Bags (http://smokymtnsaddlebags.com/).  I've not used these but Catrike owners use bags that fit in their rear frame to keep the COG lower.  
 
Also, lean into the corner with your body to help keep the wheels on the ground.  I'm sure when the Clowns get back from riding this morning, you will have more suggestions.

As Bob said, learning to lean is important, the more so as you raise the level of gravity.  On a Rover which has a higher back angle, it's easier to lean, which is good because it's so high off the ground.  A 700's back rest angle makes it more difficult to lean effectively, but it's so much lower that you almost don't have to.  Here, I am taking the corner at about 27 mph, (though the speed scrubs off quickly), and it's only my head that I lean, really: https://www.youtube.com/watch?v=T8ipMKhmPRc
 
As Bob said, you can even learn the limits, and lift at will.  There are lots of videos on YouTube showing folks "biking" their trikes: https://www.youtube.com/watch?v=gVxVo-DrCYc
 
You may do it to a lesser degree, but explore the limits of your trike to increase your peace of mind when you're in the cockpit.