Luke Summerfield, Steve Elliott and Kaid Mohamed netted in the first half and the visitors completed the scoring through James Spencer and a Michael Spillane own goal.
The Robins are level on points with Southend at the top of npower League Two and Yates felt his side were good value for their biggest win of the season.
"It's a tough place to come and we've shown that we're back on it with a professional performance and some good football," he said.
"We've made a terrific start and that helped and in the second half I asked for the same again and I got it. We were patient we moved the ball well and we did what we needed to do. It's been pleasing, we've got to take the points and move on.
"The first half performance was what we are about. We scored two goals and I didn't think they were going to get back into it."