I be Grumpy.
First off if you are trying to run a legitimate long lasting company a website is just as, if not more, importantt han a phone number. Consider getting one, they are a few hundred bucks.
Then you can sign up with services like google adwords and yahoo marketing solutions to put your website in the search engines. Also consider reading a book on SEO so you can learn how to get your site top ranked organically (free).
Next, I am losing faith in lead service providers but if you need leads fast, they are a great place to turn to... even if it's temporary. I do not vouch for any of these services but if you have money to spend they can get you leads.
www.servicemagic.com www.roofersnetworx.com www.reliableremodeler.com I currently use service magic although I threatened to quit last week and they gave me a bunch of free leads. I also use roofer networx which is pretty cheap so why not. There are a ton others and don't be suprised if they start spamming you.
Craigs list is free. Try there too. Put up a free add.
If you really want to get serious, you are going to need to put together a marketing campaign. Direct mail works well for commercial and multi family when you work it. You'll have to mail no less than 3 mailings to see optimal results. Expect about a 1% response rate on average. You may get zero response on the first mailing. I have a 1,300 mailing going out JUly 1st. It's my 2nd one to the same list this year and my 5th one to the same list over the last 4 years.
For me getting leads is not a problem. Finding qualified sales reps who can sell premium roofing is a problem.