I assume you are talking about rose bushes? First Identify the type of roses you have? This is a table I used when I first had roses.

Hybrid Tea - Hard pruning at planting time. This will encourage a strong root system and healthy shoots. Prune 15cm (6in) from soil level. Medium pruning in March as soon as signs of growth are noticed.

Floribunda - As for Hybrid Tea, but prune 10cm (4in) from soil level. Medium pruning in March as soon as signs of growth are noticed. Aim to prune some older stems to 10cm (4in) from ground level and prune only 25% of some new shoots from the lower part of the plant. This will encourage stems of different length and therefore more flowers.

Standards - Prune stems back to 6 buds. Medium pruning - try to maintain a wine goblet shape.

You are aiming to have a good shape with an open centre.
Also when dead heading them it incorporates a bit of pruning as you do it.