If you have an "A" framed roof try lining the peaks with bird spikes. Also recommended are bird gels and outdoor sound deterrents, such as the Bird Chase Super Sonic, from Absolute Bird Control. This emits distress calls and frightens the birds.
Hire a professional since you need to: 1) Follow local laws regarding killing animals (ie, poisons or trapping) or 2)climb high to install physical deterants to nests and roosting.
Wait til day when they are gone, put their nests in other trees, and block off (wood preferable, but plastic will do), every opening they can get into.
