How can I find out if I can add a bedroom to my home without violating any rules/ordinances?
Building regulations are generally controlled by either


the municipality (city/town/township/village) if you live in one, or
the county


Start with the first. Most often there is a planning or zoning office that regulates both commercial and residential construction.

Or you could consult a local builder and ask him or her what permissions you need (but double check any answer that you get; some unscrupulous builders will say you don't need any, and post construction, you may have a problem).