What was the point of putting Hawke's life in jeopardy, {spoiler]

I imagine Denzels character getting handed a rookie and him planning the whole thing so that it worked out in his favour, with whatever parameters that would look most acceptable to the investigators. He says he was planning it the whole week (in Rogers house), but also bare in mind Denzels character is a deperate man.
I sensed at the end that he really thought he'd get away with it. He didn't care at all for Ethans character so he would put him through that to save himself.

Glen's murder? Do you mean Roger?

As stated, Jake / Hawke's involvement was all about protecting them during an investigation (which always happens after a shooting). The investigator will see that Jake is a clean-cut, straight-laced rookie with a good record; so the investigator won't suspect that Jake would be part of an illicit conspiracy. That's why Alonzo wanted Jake there.

Maybe Alonzo could have got away with the shooting / robbery without Jake. But he felt Jake's involvement offered more protection from an investigation.