How can we expain the aggressive nature of Roman imperialism?

Here's what I think but I just want to know if I'm on the right track, it's for an essay.

Roman conquests were frequently excused as the necessary means to the establishment of peace and civilisation across Europe

or

They feared the others so the wanted to control all the territory so there be peace and no exterior threat to their own hegemony.

Thanks guys!

EDIT: Just noticed this subbreddit wasn't for homework help sorry about that.