Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes only.
I am a different contributor.
If your contract stated they would install a new roof, that means an entire roof, including underlay, shingles and replacing any boards as required. It does not mean resurfacing a roof in the language commonly used in the roofing trade. If they failed to do so or did a negligent job at providing the new roof, then you have grounds to sue for breach of contract in their negligent work.
As far as the bathroom, while you may have wanted a sink with an overflow, if the contract did not specify, this is going to be a bit more difficult. You would need to get an expert in remodeling rental units to examine their work and they would have to testify that the industry standard for such installations would be a sink like you describe and not a sink like they installed. If you can get an expert to testify their work was below the reasonable standard for a company providing rental renovations, you could seek to sue to make them replace the sink or for the cost of having someone else do so for you.
If they removed a towel bar, they should have replaced the towel bar and they can be liable for the cost of that as well.
You need to start by getting an expert to come out and inspect all of the work and write a report on what was done improperly and the expert will have to testify in court so you can sue the company for your damages