Once you’ve captured the rover, fly it back to the base for reconditioning and maintenance.  To release the rover, lower it into one of the empty (blue) force fields as shown in the screenshot here.

When the rover enters the force field, the field will capture the rover and it will automatically release from the recovery vehicle.  The energy field will change color to red, indicating a capture.

After the last rover has been released and all of the force fields are occupied, it’s time to return the capture vehicle to its perch.  If Automatic Landing is enabled, the recovery vehicle’s flight computer will take over and land the vehicle for you.  It Automatic Landing is off, it’s up to you to fly it back and land the vehicle on the perch where your mission began.  (The Perch is just above the first hill east of the base (to the right).)