His manager was Stefan Matschiner(Intl. Sports Agency), who was also the manager of busted top-cyclists Bernhard Kohl and Mikael Rasmussen and other now banned top endurance athletes.
Matschiner and Kohl(as well as others) already have confessed that they have used blood doping for years.
For years most of the doping happend in a blood lab in Vienna, which according to the police was a doping center for dozens of world class athletes from Europe(xc skiers, cyclists, biathletes, triathletes, runners).
Some insider put out a client list which involved several athletes who had already been caught, have confessed or confessed then as well as Simon Vroemen.
They couldn't put anyone in court cause the lab stopped when a tough law was passed last year(which puts people who organise doping in jail).The police also was not allowed to hand the data to the anti-doping-agencies because of privacy rights or something.
After the lab stopped, Matschiner together with some athletes bought equipment from them(Matschiner was also accused by pro-athletes of selling EPO, HGH and other stuff), the machines are now in the hands of the austrian police and dozens of different DNA profiles have been found as well as data that suggests that the machine has been used by a lot of different athletes lately.Kohl, Rasmussen and xc skiing gold medallist Christian Hoffmann are now getting prosecuted for organising blood doping and might face jail time.
Vroemens coach was Helmut Stechemesser, formerly active for the east germans and a close friend of Matschiner.
Over the last couple of years several of his athletes have been caught for blood doping/epo(800m runner Jolanda Ceplak among them).
According to slovenian newspapers, Bostjan Buc, who was/is coached by Vroemen, was a part of Matschiners network and involved in the whole doping mess.