My question involves a consumer law issue in the State of: Minnesota

My wife and I purchased our first home, itís a mobile home. Before we purchased the home, we had a walk through with the realtor. As we walked through, I saw water damage, brown spots, on the ceiling in the laundry room adjacent to the master bedroom. I asked what caused this but the realtor seemed clueless. All he suggested was repainting the ceiling. Before we left, he told us the roof was uneven. The ridge board, the wood beam that is the peak of the roof, seemed to have been pushed up exposing what is underneath the roof. I took this as the cause to the leaking on the ceiling.

The original asking price was $25,000. Since I liked the home, I asked for $18,000 since I would have to fix the roof. The realty company stopped me and told me they will contact their contractors and fix the roof and sell it full price. The realty company owner assured me he is doing this to protect me and himself since I can turn around and sue him if there was any damage after purchasing the home. The contractors ripped all of the shingles off the roof to examine the damage. They then replaced damaged beams/wood and re-shingled the whole roof.

Now, after 6 months, my wife and I began smelling damp dirt / damp cigarette smell in the master bedroom. We then saw a new damp brown stain in the corner of the room. With the winter weather getting warmer and snow melting, we believe it is coming from the roof. It looks like mildew rather than black mold. If I get an inspector to come and cause of the damage is due to the roof, must I pay for repairs or can I send the costs to the seller or contractor?