Today I was prescribed desyrel (trazodone) for my supposed insomnia to help me get better sleep. Is it okay if I take this at night in conjunction with zoloft?

Depends on the dose. Usually both are compatible with a smaller dose for the desyrel (trazodone). It may enhance the effectiveness of treatment in 2 ways by a direct chemical effect & by just providing for better sleep.
Trazodone/zoloft. Both are antidepressants belonging to different group, and can be used together, with low dose of trazodone being given as add-on to help sleep.
Yes. Both medications affect serotonin and if someone is on too many serotonin drugs they can become confused, sweat too much, become restless etc (see serotonin syndrome) however with just the zoloft and Desyrel (trazodone) this would be exceptionally unlikely. We combine the two meds all the time. I hope you sleep well!