How do I get roofing leads when I have almost no marketing budget?

If your budget is close to zero, start with the channels that cost time instead of cash. Call every past customer, ask for a referral and a review at the moment a job passes final inspection, and get your Google Business Profile complete with current service areas and real photos of real jobs. Those cost nothing but discipline and they raise the floor. What they will not do is fill a calendar on a schedule, so treat them as your base, not your pipeline. When you are ready for predictable volume, Lead Engine books at least 6 shown residential or 4 shown commercial roof inspections a week, month to month, with pricing scoped to your market size and inspection volume on a 30 minute call.