You should have had him bring the warranty when you paid him.
Anyway, do you have an invoice showing the brand and type of shingle? Do you have a wrapper from any of the shingle packages?
Either will allow you to go to the manufacturer's website so you can download the warranty.
What's left is the roofer's own warranty for the installation. Roofers don't give much of a warranty on the installation, usually a year.
If you didn't get it written on the invoice and he's already been paid you can pretty much forget getting it now, unless he's licensed (is he?) and you can put some pressure on him that way.
Or you can write him up on Yelp and/or other local review sites, warning people to get the written warranty from this roofer before handing over the payment.
The lesson: A manufacturer's warranty comes with the product. An installation warranty is something you negotiate with the contractor and you'd better get it writing before you pay him.
Anticipating my fellow pedants reminding me about warranty laws, they do exist but they don't help much with an unlicensed and/or un-reputable contractor.