The 19-year-old midfielder has been in north London for the past three years, but after failing to break into the first-team is considering his future away from England.
Out of contract at the end of the season, Spurs boss Andre Villas-Boas must make the decision on whether or not to let the youngster leave White Hart Lane now, or allow him to walk away on a free next summer.
His chances of regular football with Tottenham are highly unlikely, and so Troost-Ekong flew to his native Holland to train with RKC for a few days.
The Eredivisie outfit's chief scout, Janus van Gelder, hopes a deal can be struck for the Dutchman, although he appreciates that what happens next will be determined by the Premier League club.
"The cooperation was liked by both sides. We want to add William to our squad," he told Voetbal International. "However, we are dependent on Tottenham. We don't have the financial resources to sign him already in the winter break.
"For his development that would be the best solution as he has to play more minutes. We have to wait and see how the situation will develop."