How to go about this?

I just bought a house and within three days the drain in my garage started over flowing. I called the plumber and discovered roots in my line. I was very frusterated because 2 weeks earlier on the disclosure the previous owner said "no known drainage problems". The plumber was my neighbor and said he had been there before and diagnosed this before. Well I'm not an uppity person, and they had just had a baby so I blew it off, paid for a new line and moved on. Well my bathroom line is now stopped (seperate lines). The plumber said roto rooter had been in the yard messing with that one. I called them and they told me they couldn't give me any information on that. First question, are they really not allowed to divulge information? And second are they if I do decide to take action. (In addition they were to have an a/c serviced, and they didn't and I had to buy a new one 9 days after purchasing the home)...man I got screwed!!!!