Like every other question related to cost, the answer will depend on several factors. Regarding roofing, the cost will depend on factors such as the size of your roof, the scope of your project, preferred roofing material, ease of access to your roof, roof accessories, e.g., chimney, and the roofing contractor you choose. The average cost of a shingle roof is $5000 – $15,000, while that of a TPO roof in Gaithersburg will be between $3.50 and $14 per square foot.