No. The Let's Encrypt root was recently created and will be submitted to root inclusion programs. It will probably be quite a while until its suitable to issue certs solely from the Let's Encrypt Root.

For now, the certs are cross signed by "DST Root CA X3" operated by Identrust. This root has very strong inclusion.

For specifics, please see: https://groups.google.com/a/letsencrypt.org/forum/#!msg/clie...

They're cross-signed by DST Root CA X3 which is in the list.