The Knock Out roses are also known as a "Self-Cleaning" rose bush in that they drop all their petals and send out new blooms without having to prune them to bring on the new blooms. Usually they will have buds coming on strong for another cycle of blooms once the old blooms have fallen off. If it has been real hot where you are or even windy, they might need some watering. Keep an eye on the soil moisture and perhaps give them a foliar feeding with some Miracle Gro to give them a boost. The blooms should return in grand fashion soon.