Hermelyn, 21, hit .321 with a career-high 12 doubles, six homers and 49 RBIs this year for the Sooners. He said he'll report to Tri-City next week after he takes his physical and signs with the club and helps add to the team's catching depth in the Minor Leagues.
"I'm really excited," he said. "This is a goal, and for it to actually be here, it's pretty cool to hear your name called. The whole family was watching the computer and what an emotional moment. It's like, it's time for me to start doing what I want to do."
Freeman, 23, signed his contract on Thursday and will report to full-season club, Class A Quad Cities. He was named the Big 12 Conference pitcher of the year after finishing his senior season with a 10-3 record, 1.31 ERA and 97 strikeouts in 109 2/3 innings.
"This is every kid's dream to get the opportunity to play professional baseball, the opportunity to compete for eventually a job at the big league level," he said. "The opportunity I'm really thankful that the Astros have that faith in me and really believe in me and want me to be a part of their organization."
Weathersby, 23, was used primarily in relief this year at the University of Mississippi, going 4-2 with a 2.62 ERA in 17 games (four starts). He said he'll go through a physical soon in Florida and report to Tri-City soon after signing his contract.
"Growing up, you're playing catch in the backyard with your parents and you're coming through Little League and high school and stuff like that, so for me, signing wasn't just about me," he said. "It was all those who helped me to get to where I am and I'm forever grateful to them."
Because he played three years in the SEC, Weathersby is very familiar with LSU shortstop Alex Bregman, who Astros took with the No. 2 overall selection.
"I got asked earlier this year by some guy, 'You know you've faced a lot of people, but who's the best hitter you faced in your college career?'" Weathersby said. "I said Alex Bregman. It will be cool getting to play with him because I've seen the talent and the completeness he's had to have success ever since he's been at LSU."
McCanna, 21, had a 3.13 ERA in 218 2/3 career innings in his three years at Rice, and this year finished among C-USA league leaders with seven wins, a 2.96 ERA and 85 innings.
MLB.com reported Thursday the Astros had agreed to terms with fifth-round pick Trent Thornton, a right-handed pitcher from North Carolina, and catcher Garrett Stubbs, an eighth-round pick from USC. The Astros have five draft picks competing in the College World Series: Bregman and teammate Zac Person, a left-handed pitcher; right-hander Thomas Eshelman (Cal State Fullerton); pitcher Riley Ferrell (TCU); and third baseman Bobby Wernes (Arkansas).