Ladders are only to be employed as a last resort, and for tasks that are low risk and short in duration, thus, this is correct.
Additional certifications from the roofing contractor you hire are usually a plus. For example, the SafeContractor plan or membership in the National Federation of Roofing Contractors can provide this further layer of security.
Your landlord must comply with the terms of your rental agreement. Your landlord is generally responsible for maintaining the structure and outside of your residence, including the walls, roof, foundations, drains, gutters, and external pipes, windows, and exterior doors.
To make a roof watertight, roofers put down shingles, asphalt, metal, or other roofing materials. Roofing contractors install, replace, and repair roofs utilizing materials such as shingles, bitumen, and metal.