Cost of the roof repair depends on a few key elements and once you are aware about then you will be able to estimate the cost yourself to be able to draw a budget to give to the roofing contractor rather than just wait for a quotation.
Firstly you need to be aware of the roof type and the materials used on the existing roof. You also need to be aware of the slopes and pitches as labor costs depends on that along with the what kind of work you will get done. When we talk about materials shingles will be cheaper than slate and slate would be cheaper than clay tiles and so on. Also, a lot of variance in pitch and multiple slopes will increase the labor cost.
How much repair is necessary to save long term costs. We usually ignore or delay repairs and maintenance when we spot a damage and this may lead to bigger expense in not taken care of immediately. Inspect the roof yourself and fix minor things that you can. This will reduce the work for a roofing contractor and in turn will reduce the amount you spend on the roof repair
Lastly you need to find out about city permits for specific roof work you need to get done. Some cities require additional construction or repair permits even for roof repair which the contractor will add in the bill and it is highly likely that the roofing contractor will include his time and resource cost, you can cut that down by getting the permits done yourself.