Every single answer here is failing to address one thing: The Oxford comma. Some argue it's necessary, others say it isn't. As a journalist, we are taught to NOT use the Oxford comma and instead follow what AP Style says to do. That is, we leave out the Oxford comma.
Also, there seems to be some serious confusion about the first one.
If people put the semi-colon then it appears a room is missing. Writing, "This house has three rooms; a kitchen and a bathroom" makes it look awkward. With a semi-colon you are looking for what that third room is. If it's written, "This house has three rooms, a kitchen, and a bathroom" that makes it correct (with or without the Oxford comma). Or if you wrote, "This house has three rooms; a kitchen, bathroom, and dining room" that would also make it correct.
The word that seems to be throwing people off is rooms. It's ambiguous because a kitchen and a bathroom ARE their own separate rooms, however, this sentence appears to be mentioning the three BEDrooms in addition to the bathroom and kitchen.
The second two are both correct based on whether you use that pesky Oxford comma. If you're a journalist who follows AP Style, chances are high you won't. If you are in an English class, chances are high you will.