You can make your own dog kennel roof using 1"3/8 top rail tubing sold at Home Depot in 10'6" lengths.  They also carry tarps or Harbor Freight Tools has a great deal on their silver tarps.

Ridge pole roof

Dog Kennel roof ideas using Chain link fencing parts

If your kennel is 6' wide we recommend an 18" or taller center post this works out to a 6 inch drop in 12 inches otherwise known as a 6 in 12 pitch.  This is the minimum recommended slope.

Ready Products LLC

Readydogkennel. com

The taller the center ridge the less chance of water pooling up which could collapse the kennel and injure the animal.

Never span more then 10' without additional support .