Oh, shingle textures in Photoshop are easy. Or bricks or whatever have ye. It's all about BRUSHES.

Go wander off to a texture site like http://cgtextures.com/ and download some shingle textures. Open them into Photoshop. Go to EDIT, then DEFINE PATTERN and save it as a pattern. Now select your brush tool. Open up the brushes tab (shortcut is F5 in CS2) and look at the dropdown. There's one that says 'texture'. Click on that, not on the checkbox (check the checkbox too) but on the word that says texture, which will bring you to the textures menu. There's a thumbnail with a little arrow beside it. Click the arrow, scroll down, and pick your newly saved shingles texture. Now your brush is a shingle texture and you can draw with it over top of your gradient to get a texture.

Other options include drawing some shingles by hand, or with the mouse or a tablet, saving them as a brush and using it as a stamp.

So you can always use the gradient tool to set down a gradient and draw overtop of it with a texture.