@nsharath
If your solaris server does not have grub password then, you can edit the grub menu and then drop in to single user mode without root password, then use passwd command to reset your root password. This works in unix, so should work in solaris also.
Also if you can connect to the mngmnt console behind the server using a laptop(tftp) like how u connect to a switch or router, you can reset root password from there also I suppose...Please google on that...