After boarding the starship again, Roy was not in a hurry to leave the Void. Instead, he got Rafaro to find a random direction to fly in. As for how long he would fly, Roy didn't tell him and only pondered by himself.
He had no other purpose in doing this. He just wanted to see if he had the luck to find another Void Lord in the Void.
Although Lilith had said that there were thirteen Void Lords in the Void, Roy had only found one so far. It was the black sun-like Void Lord that he and Sargeras had seen together. He only knew the location of this Void Lord.
The Void was too big. It existed in the background of all the worlds in the Infinite Worlds. Even if there were thirteen Void Lords, they might be extremely spread out in the Void. If Roy wanted to find another Void Lord in this universe, he might have to run more than half of the universe in the real world, which might be billions of light-years away.