I figured it was a planet harvester like that ship in "Dead Space" and that is why it had powerful weapons. I also believe since teh Romulans are a warlike race, they would pretty much arm everything in case they need it in time of war.
True. A human looks at a mining ship and says, why does it need weapons and armor? We're not planning on taking it into battle." A Romulan looks at it and says, "Wait a minute, if we get into a massive war and are depending on ships like this for raw materials to fund the war effort, our enemies could attack our lightly armed mining ships and cut off our supplies, crippling our fleet without ever engaging them. Arm that thing to the teeth!"