I am a handy, capable person when it comes to building, plumbing, electrical, etc. But, what I'm not is that creative so design isn't my foray. I want to do a large room addition to my house with a rooftop deck and finish a part of the attic. Outside of hiring the concrete pour, mason, and getting my ac guy to redirect duct work, I want to do most the work myself.

Where/who can I hire to draft plans for me and also give an overview of things to expect? I live in Conroe, but outside the city limits with a couple of acres.

Hire a reasonably priced architect by-the-hour that does ONLY residential work, a small office is best.
https://indreg.tbae.texas.gov/Reports/IndividualSearch

You WILL be doing more of the work ... homework and directions, just not the hands-on design/drafting where you can do the most damage & thus years of regrets.
Top architects use SF budgets NOT $$$ ones
but the both of you glean $$/SF construction costs prior to designing.

You'll save money if you can provide Plans to the current house to avoid redrawing it.

Thank you for that! With that and a buddy that's a small contractor (who's booked 6 months out!) to help with tips, this would be exciting!