Kimberly Cheatle -- the director of the Secret Service -- put out a statement Monday that somewhat addressed all the scrutiny that's been directed at the federal agency after Thomas Matthew Crooks was able to get up onto a roof outside the PA rally and fire off shots at DT.

She says, "The Secret Service is working with all involved Federal, state and local agencies to understand what happened, how it happened, and how we can prevent an incident like this from ever taking place again. We understand the importance of the independent review announced by President Biden yesterday and will participate fully."

Cheatle says she understands that Saturday's incident has led to questions about potential updates to security for the convention -- which kicks off in Milwaukee Monday -- but that despite all the concerns ... she says the Secret Service is all set to do their job.

She adds, "I am confident in the security plan our Secret Service RNC coordinator and our partners have put in place, which we have reviewed and strengthened in the wake of Saturday’s shooting."

Cheatle says that they've already tweaked Trump's security detail, in light of what happened ... not to mention President Biden's order to review Secret Service processes.

She finishes by saying, "The Secret Service is tasked with the tremendous responsibility of protecting the current and former leaders of our democracy. It is a responsibility that I take incredibly seriously, and I am committed to fulfilling that mission."

As you know ... the Secret Service is catching heat for what many are calling a serious lapse in security -- wondering how Crooks could've possibly gotten into position with a rifle so close to the ex-Prez.