When you get onto the roof at the crane you will see a fence.

Instead of activating the crane jump onto the box with the gas canisters, hop onto the the thing next to it and onto the fence.

Then, get a running start and jump onto the next fence (the jump is kinda tricky but keep trying)

Then turn towards the roof your supposed to get onto,get another running start and aim for the corner with the electrical stuff.

If you make it you can easily jump onto the roof and continue on your way (just keep jumping at the corner of the roof).