When buying parts on bricklink, is there any way to bunch of a specific type (ex. Red Roof pieces), or do I have to go through and pick the pieces and quantities individually?

Try "Wanted Lists"

In this case, it might be more help to know what you want to do. For example, if you're replicating an existing set (or a MOC that appears on rebrickable.com), you can automatically generate a Wanted List from the parts in that set/MOC, and then search stores for items on your wanted list.

That should get you the correct number of each of the different parts you need.

If you just want a generic collection of something like "Red Roof Pieces," (which I'm assuming means red slopes?), then it's not quite so easy, and you do have to do a little bit more work. You could create a wanted list, picking the parts individually - you'd have to pick every type of "roof" piece you were interested in, and add to your wanted list, including specifying the color.

There have been roof packs (like this one) that you could part out to a wanted list, but it might not include every variation of slope.

Maybe, try playing around with the advanced search.

It's not very intuitive, but you can use it to find stuff like 'all red slopes,' ones with specific angles, curved.. good luck!

As an aside, text searching can also be handy if you are looking for things that have different part numbers (or moulds) but are otherwise substitutable. They have elements of the same name, but not the same part number. To do this in wanted lists results in lots of duplication and you need to keep track of how many of each you are wanting.