Roberts has handed in a transfer request and is expected to join City on a deal worth around £11m.
Symons had hoped the 18-year-old would continue his education at Craven Cottage, but he revealed a transfer was moving closer after their 3-1 pre-season friendly win over Crawley Town on Saturday.
“It’s very difficult,” Symons said. “He’s handed in a transfer request now and he’s only got one year left on his contract.
“We want to keep all our best players and build for the future but there comes a point where that becomes very difficult and you have to do what’s right for the football club. It’s progressing it’s fair to say. He’s in serious talks so we’ll have to wait and see.
“It’s a shame to lose one of our bright young talents but I need to have people that are committed and want to play for the football club.
“I sat down with Pat and his parents and told them how much we value him and want him.
“But they’d made their minds up and it then becomes quite difficult. We did all we could to keep him but good luck to him if this is what’s going to happen. We’ll move on, this is a big club with a lot of good players here.”