In the end, Rovers had to reject the Popov deal as Roberts remained.
Williams told the Lancashire Telegraph: "We were confident he would be fit and ready to fight for his place if he was still with us, but deep down I think we wanted a move.
"The problem was we couldn't let him go without a replacement. Four strikers are needed. We covered our position with Ivelin Popov ready to come to Rovers.
"His club knew the deal was dependent on Jason leaving but in the end no bid came."