Default SSH user
A better solution than putting an alias in your bashrc, would be to use a ssh config file
cat ~/.ssh/config HOST * USER root
You can also specify certain subdomains use certain users. Useful if your laptop travels between networks.
HOST 192.168.*.* USER homeuser HOST 10.2.*.* USER workuser
You could even configure by domains, and use different ssh keys for different domains.
HOST *.microsoft.com USER bill IdentityFile ~/.ssh/microsoft/id_rsa HOST *.apple.com USER steve IdentityFile ~/.ssh/apple/id_rsa