We don't support uploading the realm keys through the admin console at the moment. However, you should be able to use the admin endpoints to manually set it. Should be relatively easy to add though, so you can create a JIRA to request it, but you're actually the first to request it.
With regards to clients we don't have an elegant way to deal with this. What we have is if the public key is not specified in the client config it will download it from Keycloak at startup, so if you restart your clients after creating new keys it should work. Ideally Keycloak should send a message to the clients to notify them that the keys have changed so they can re-fetch from Keycloak, but that hasn't been implemented yet. Again, feel free to request that.