Most likely to be 'Black spot' (need photo to confirm though) if so no you wont loose them if treated regularly, you can buy sprays to control this.
Spray all your roses at the same time when the weather is dry and not windy to reduce spread of disease, also remove affected leaves and dont let them fall to the ground. Feed as well to make sure they are not short of nutrients which can also produce problems.

And next year spray with Roseclear or similar before the spots appear. Pick up all the spotty leaves that have fallen as the spores overwinter on them and will reinfect next year. (Sorry Drc, just noticed you advised that already)