We could have a TLS Test with RSA PKCS#1 format support. It is unsure the TLS Tests available uses PKCS#1 format but as per comment in few of SSL*Template.java it uses PKCS#8 format.

Here is a way to identify format. Similar header applicable to PublicKey too.
PKCS1 private key (unencrypted) in PEM looks like: -----BEGIN RSA PRIVATE KEY-----
The same key in PKCS8 unencrypted: -----BEGIN PRIVATE KEY-----