It's all true about Teddy's life. I'm not embellishing. With his first wife passing away like that when his baby daughter was 2 days old, and him leaving her with his older sister and leaving the east to go into the frontier....my imagination is in overdrive. I don't know if they could find an actor to mimic that highbrow, upper New York Knickerbocker type accent that the upper classes all had. If you listen to a recording of Teddy's voice on youtube (he made a recorded speech in 1912), his high pitched voice will surprise you. It's not "rugged" and macho by today's standards at all. Also, Teddy was pretty short, only about 5 feet 8 at the most. Still, here he was--this hoidy toidy New Yorker with his thousand dollar cowboy outfit he had specially tailored, going out there in the West with the local cattlemen laughing their asses off at him. 2 years later, after he managed to bring in some local criminals that were on the run for robbery, Teddy won every one of them over. They all respected him even though they thought he sounded hoidy toidy.
Lincoln with his height, his eloquence and his well documented extraordinary physical strength as a young man was the easier choice for incorporating into a story such as this, no doubt. Teddy Roosevelt was so asthmatic and skinny as a child that they feared he'd never be healthy.