When a DER format RSA private key is extracted from an encrypted PEM file, is it still encrypted? Let's pretend we create a passphrase protected PEM file using openssl:

$ openssl genrsa -aes256 -passout pass:password -out sample.pem 2048


And then extract the private key in DER format:

$ openssl rsa -in sample.pem -out sample.prv.der -outform DER


Is sample.prv.der still encrypted using the passphrase?
No, it will output the PKCS#1 compatible encoding of the private key, try this:

openssl asn1parse -inform DER -in sample.prv.der


it will output an ASN.1 sequence of:


a version number (00);
the modulus;
the public exponent;
the private exponent;
the CRT parameters.


It did ask you for the password, right?