Rocks had gone into the game with a one-point advantage from the first match, but had no answer to Cameron Rundles, who hit a game-high 36 points.
Harrison said: "They were just better than us. All the hard work we did in the first leg went out the window."
SPEEDWAY: Glasgow Tigers went down 46-44 against Leicester Lions as they began their defence of the Premier League title.
CYCLING: Britain's Mark Cavendish won stage two of the Giro d'Italia, starting and finishing in the Danish town of Herning.
WOMEN'S FOOTBALL: Glasgow City kept their place at the top of the SWPL with an 11-0 win over Inverness at Petershill Park. Celtic slipped to a 1-0 defeat at Forfar Farmington, while Rangers drew 1-1 at Kilmarnock.