Roof timber and venting

Having had a bit of a poke up on the roof of the new house over the past few weekends, I've found a couple of things that need fixing. First, timber. The wood that the tiles hook over in one spot isn't the same as the rest, nor is it fastened down. It looks like this was done after someone put the rangehood vent in. What sort of timber do I need to buy to replace it with? I presume it needs to be treated? Second, the extractor fan in the bathroom just blows straight into the roof. There...

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