This image from the Illustrated London News in 1907 speaks for itself.
The caption reads:
Football on roller-skates was inaugurated recently for men at Brighton skating-rink, and the pastime was very soon taken up by women. The game is played six a side: there are three forwards, two backs, and a goalkeeper. The goals are six feet high and seven wide, and the regulation football is used, with a little over a pint of water in it to keep the ball from rising. Twelve feet in front of each goal is drawn the penalty line. Down each side run the boundaries. When the ball gets into touch it is not thrown in, but is placed on the boundary line, and pushed into play with the side of the foot. Hustling is allowed, but not charging. Outside his own penalty area the goalkeeper must not handle the ball. Two minutes is allowed to repair skates.