Venting Bathrooms and Dryers through the Roof

Straight up. That's what the vent needs to do. Elbows in vent piping cause pressure and give the gases being sucked out a potential place to leak.
The lowly bathroom vent mainly pulls the water vapor from the bathroom after hot showers but we lovingly refer to them as fart fans. You can imagine why. The same applies to sewer stacks: the stink stack. Imagine those attached to septic tanks. Now you don't want to be using a flame thrower to install an SBS modified bitumen system. Torches in the hands of roofers?
They never found those roofers in San Antonio, or so goes the legend.
The dryer vent is even more temperamental. If you cannot find any other way to send the dryer lint and exhaust horizontally to a wall exhaust, then up up and away you must.
With time, no matter how often you clean the lint basket, the tubing will clog and you'll steam your clothes. If there are elbows the clogging will accelerate. If you run the dryer during rain, you'll put a stop to lint removal right away. Besides when the humidity is high, like when it's 100% during rain, it is not a good time to dry clothes.
Bathroom fans are on the ceiling but you'd be surprised how many just dump the water vapor into the attic where a sponge called plywood resides. Run it out and through the roof.
I've seen enough lint on attic floors to insulate part of a home but you must remember that lint is very combustible. Many a belly button has spontaneously exploded due to improper gas venting.
The roof/dryer vent flashing is a lot like the one that goes on the wall but it has a flange that can be integrated with the roof. The flashing has a swinging door that helps keep out rodents.
Don't forget to remove the screening or the lint will cling. This screening is only for bathroom vents.
If it takes an Act of Congress to get the dryer vent to an outside wall then so be it. Running one upwards requires diligence. Check to see if it is stopped up often but you need to check the horizontal one too, just not nearly as often.
Here's a good money saving and environmental green tip: let your clothes mostly dry on some hanging apparatus prior to placement in the dryer. You'll use less electricity, your dryer will last longer, you'll cause less pollution, but mostly your clothes will last longer. That spinning in high heat cooks your clothes. What do you think the lint is: clothes.
I use soft water so I need very little soap, one ounce per load, and no fabric softener. That stuff goes into your system through skin contact and through inhalation. You smell it and you absorb it too.
Saving the environment can be as easy as lots of accumulated small tricks and if they save you money too then it is a win win situation. And it pays to look snappy by not wearing out your favorite shirt or blouse.