Saying he was an investor, Manoj Sharma waited for Roy to emerge from a vehicle near a Noida courthouse and threw the ink at his face, the Press Trust of India reported Tuesday.
Shama shouted "Sahara chor hai" (thief), at Roy before throwing the ink, witnesses said. He was roughed up by some lawyers and was removed by police.
Roy was at the courthouse for a hearing after he failed to appear before the court in a case arising from two of his companies not refunding money to investors.
Two other directors have been arrested.