How could we explain the aggressive nature of roman imperialism?

They feared the others so they wanted to control all the territory so there be peace and no exterior threat to their own hegemony or Roman conquests were frequently excused as the necessary means to the establishment of peace and civilisation across Europe.

I have to do an essay and I never did one before, this is my statement for it I just want to know if I'm on the right track thanks! It's a 1200-1500 word essay for introduction to western civilization class.