The most common cause of bumping fish on a running line is allowing a bow to form between the rod-tip and the float, so when you strike, you’re not direct enough to the float and the fish aren’t hooked properly.
Longer rods and silicone line spray on your reel can help solve this.
Another issue could be hook size. Try going up one size, a 16 for double maggot and an 18 for single, for example.
Soft, tip-actioned rods are vital for roach.
Learn the perfect roach stick float rig by clicking here.