I have grown Knockout roses, but I can't remember anything about their fragrance.
As long as it has a fragrance, you can make rosewater from any rose. The strength will vary, depending on the strength of the rose's scent, and you might need more petals from a rose with a light fragrance.
If you like the scent of Knockout roses, you will like the scent of rosewater made from them!
You can make rosewater from any rose, but the fragrance will be the fragrance of that particular rose. Some roses have little to no fragrance, some have a light fragrance, some have a more complex fragrance, and different varieties have subtle differences in their fragrance. For example, the Damask Rose fragrance is subtly different from the Centifolia Rose fragrance.