two possibilities. If you have enuf wind, you might be able to change the tow point on the Roto's bridal to get it to fly a little steeper.
I think the all-time champ for flying at a steep angle is the Roller Kite, also know as Pearson's Roller. It is very stable without a tail so you can easily tow another kite as line laundry. It has great lift and takes off from the ground like a rocket. Often flies almost right over head. It was designed for an English club that flew in tight quarters in little London parks.
Give it a try.