Williams is pushing for his first start when the Shrimps travel to York after two scoring cameos from the bench, including last weekend's dramatic late winner against Dagenham.
The midfielder has trained with Morecambe since the summer but clearance issues prevented him from signing professional terms until earlier this month.
"He's had a massive impact," Roche told Press Association Sport. "He's been with us really since the start of pre-season and he's come in each day working his socks off knowing that he wasn't going to be able to get a deal until maybe January.
"So he's been coming in off his own back not getting paid and he's worked really, really hard.
"Given the chance when he's got it he's taken it and been absolutely brilliant. He's scored two very good goals but also Saturday's goal was so important to our season."