I'm a landlord in Colorado and in my lease there is a clause that covers this I believe. If I were you, I'd make sure you have written communication (emails, not texts!) to the landlord to confirm they 1) agree this is an existing issue and 2) they agree to resolve the issue prior to move in (be specific) and 3) if it arises again while you're a tenant, you won't be held accountable as the "cause" of the infestation. My lease states that any infestation issue after 10 days or so is the responsibility of the tenant.
Here's the text in my leases: Pest control, after the first ten (10) days of the Term of this Lease, shall be the sole responsibility of the Tenant, including, without limitation, prevention and remediation. Tenant shall keep the Premises free of all pests, including without limitation, rodents, fleas, bed bugs, ants, cockroaches, gnats, flies, and beetles. Tenant shall pay for all costs associated with remediating pests from the Premises and shall inform Landlord at first sighting of any pests in order to avoid any infestation of pests. In signing this Lease, Tenant agrees that Tenant has examined the Premises and certifies that it has not observed any pests in the Premises.
Did your lease have anything similar? Did you already sign stating that you did not observe any pests? These might be factors but I'm not a lawyer, so I can't advise.
Otherwise, you might seek legal advice/support or refuse to move in or pay rent until the issue is resolved. If the landlord doesn't address the issue, you might be able to seek what's called constructive eviction (basically you evict yourself and terminate the lease) if the landlord fails to perform per the terms of the lease.
Good luck! And please update here with how everything shakes out.