extension ladder

So I need to get at a downpipe that has come loose from a dormer bedroom extension. However, the ladder would need to be placed on a gently sloping roof over a kitchen extension. I'm thinking of siting a telescopic ladder in the 'trough' created by the Velux window (see blue arrow in photo.)...

Looking an extension ladder to use around the house, im looking for a double extension 2x12 rung, which of these two would be best? https://www.youngmanaccess.com/extension-ladders/Trade200Series/57011318 https://www.wernerco.com/eu/extension-ladders/722Series/7223518