Did you know there are 15 NFL regional combines that pay no expenses and actually charge each participant $295 to enter?

"I didn't," said former Gophers defensive tackle Roland Johnson. "But my brother did some research. I've been an underdog my whole life, so he went online and looked up how to make the NFL. And that's what popped up."

Johnson advanced from the Miami regional combine to the super regional in Detroit to a three-day tryout at the Vikings' rookie minicamp this week. Joining him on the same path as tryout invitees were Northern (S.D.) State offensive lineman Jon Caspers, Sul Ross (Texas) State cornerback Randell Carroll and Minnesota Duluth safety Jason Carlson. Villanova defensive end and fellow regional and super regional survivor Rakim Cox was signed as a rookie free agent earlier.

"It's not cheap to pay your own way to get this far," Johnson said. "My mom [Rochella] and my brothers [Ryan and Marvin] paid for me. Thank God for moms and brothers."

Cox's agent, Christina Phillips, footed his bills.

"She knows I should have been drafted," Cox said. "It got to the seventh round, and no team would pull the plug. It was a slap in the face. But I use it as fire on my wood."

Regional combines have been around for years as a stage for overlooked prospects. But only in the past four years has the NFL stepped in to organize them and establish the ensuing step, an invitation-only super regional combine, sans entry fee.

A year ago, 29 super regional participants made NFL rosters, including Vikings practice squad players Adam Thielen and Bradley Randle. Ten made an opening-day 53-man roster, while six saw game action.

"The super regional is pretty competitive top to bottom," Carroll said. "But my regional combine in Baltimore? This one dude was about 38 years old. He came in talking trash, but he didn't make it past warmups. He was throwing up all over the place."

Randle said he saw something similar in Los Angeles.

"There was a guy who was 5-11 and probably 270 pounds," the former Viking said. "He had a big old gut and he's about 30. Said he was a fullback. Maybe in middle school."

NFL scouts don't attend regional combines. Pro scouts Ryan Monnens, Scott Kuhn and Jeff Robinson represent the Vikings at the super regional.

"You're probably not going to see a complete player," Monnens said. "What you're looking for is that one redeeming trait. It's also good for the small-school guys who don't have verified height, weight and speed. Or they have very little quality game tape."

Speaking of which, Carroll assumed modern game tape wouldn't be an issue when he transferred from New Mexico State to Division III Sul Ross State in Alpine, Texas.

"But our film guy was pretty bad," he said. "Sometimes, I wasn't even in the shot. And he didn't have a tripod, so sometimes you saw more of the dirt in front of him than you did me."

A year ago, Thielen paid about $3,000 to train for and attend the regional combine in Chicago and the super regional.

"I had to use my student loan money," said Thielen, a Detroit Lakes, Minn., native and former Minnesota State Mankato receiver. "But it was worth it."

Thielen participated in last year's rookie minicamp as a tryout invitee. He was signed and spent the entire season on the practice squad, which pays a minimum of $6,000 a week, or $102,000 for the season. He's still fighting for an active roster spot that would pay him $420,000.

"I actually had an internship all lined up with Patterson Dental," said Thielen, a business major. "I was set to start a week after rookie minicamp. I had to call them and tell them I couldn't make it because the Vikings signed me. They knew my situation, but that was still kind of a strange thing to have to do."

Mark Craig • mcraig@startribune.com