Is this a leaking roof tile?

goldbyron

I have a third floor (converted loft space) flat and just found a brownish liquid in a stream and small puddle in my bath. I examined further and the ceiling (which is wood planks -don't ask - it was there already:)) was slightly wet in the part above the bath and leak. I am thinking the liquid was rain water discoloured by old varnish?? It last rained heavily on Sunday so it may have been after then but didn't notice until now. Thinking a leaking roof from a slipped tile? Any thoughts before I call a roofer out to prevent being ripped off? Thanks