Does Route53 let you manage the DNSKEY RRset (so you can add a DNSKEY to the set yourself) or do they have some sort of facade you have to interact with instead?
Route53 signs the zone itself, and the key is managed using AWS KMS.
That's an answer to a different question. I asked if they let you put a DNSKEY RR in the RRset they serve. (To be clear: I'm not asking if they will import private keys and sign with them or anything like that, just if they'll let you place an additional DNSKEY in the RRset they serve.)
I had to add a DS record to a Route53 zone just the other day, and when I did, I didn't see a DNSKEY option in the list of records. Don't count on that 100% because I wasn't looking for it, but I definitely don't recall seeing it.