Those trades mostly pay their dues when they are younger and then the next batch of journeymen and apprentices take over that part of the job as they move up into the less physically demanding parts of the job. Even fairly physical jobs like bricklaying, they'll have the older dude doing nothing but slapping the bricks in place, they get carried over to him by one guy, one guy is mixing up the mortar, one guy is unloading the truck, another is touching up the joints, etc. It's one of those things that explains why union jobs have so many extra people too. It's not one dude doing everything, it's 3 guys doing different parts of the job and learning how to do the next part.
Like, tying rebar is really hard to do by hand, but they make a gun that will do it for you in seconds: https://amsalesinc.com/products/rebar-tying-gun-makita-xrt01... . You can do a whole pad of concrete in an hour that would take you days otherwise. But that gun is thousands of dollars (supply and demand baby). So having a truck of these time saving gadgets for a bunch of job types isn't feasible. Hence the specialization.
[0] who then never shows up on time and charges too much. But that's a whole nother story about where I live...
Roofing might be relatively worse than electrical, but both are definitely harder than sitting an air-conditioned desk.
your other option is mentally drained, potentially depressed, probably anxious - especially if/when something breaks on you
i went with the desk job, yearn for something else.. would rather have become a machinist or welder looking back. do both as hobbies now to clear the head from the desk job