If the rent includes the use of the rooftop as you say, then subject to the Agreement, you would usually have exclusive use of the rooftop.
There could be issues of trespass and breach of implied covenant of quiet enjoyment depending on the content of the contract. In general, according to common law principles, unless otherwise specified in the lease, a landlord has the implied duty not to directly or indirectly interfere with or affect the purpose for which the property was let to the tenant and his reasonable enjoyment thereof. However, whether your case has a good prospect of success also depends on whether the landlord is making necessary repairs and has taken all reasonable steps to prevent the annoyance.
At the very least, if the landlord in repairing one part of your flat has damaged another, the very least he could do is compensate you.
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