This is the walkthrough from the Empire side using mostly HQ7 units.
Roolan's Wrath - Mission 19 (3 Stars)
http://youtu.be/aBQJjCUvwk0
Roolan's Wrath - Mission 20 (3 Stars)
http://youtu.be/H74wEdy6dk4
Roolan's Wrath - Mission 21 (3 Stars)
http://youtu.be/qunza99cv3E