"Steamroller" to describe a person as very determined

"Like a steamroller" is acceptable usage for describing a person. Dictionary.com (Collins) cites one meaning of steamroller as "an overpowering force or a person with such force that overcomes all opposition." The New York Times has many examples where people are described as such. Here's one: "the 6-foot-6, 245-pound Worrell, who played like a steamroller last night." Another: "Oprah came on like a steamroller but he is not showing any attrition." Sylvia Plath wrote "I need a strong mate: I do not want to crush and subdue him like a steamroller."

Probably not the best choice "steamroll" as a verb generally means to push through some process/solution crushing all opposition

"Prime Minister Harper intends to steamroller his elimination of...."

"Tories: we'll use ancient laws to steamroller through welfare cuts"