Default [Q] root custom rom

i downloaded custom rom for my spice mi 353 gone well and flashed through fastboot.
booted well but camera didn't worked no problem for that. it was having superuser access and i unpacked it with unyaffs in linux and do some modifications for camera and repacked with mkfs.yaffs2.x86 and flashed it .now the camera is working but no superuser access available now. i just checked if i did some wrong by unpacking original custom rom file and repacked(nothing touched,packed as it is) again no superuser access.hi checked in super user there is a line in info under su binary v3.1. as "-rwxrwxrwx" now it is in red color but earlier it was green when rooted.
pls help me how can i gave root access to my modified rom. ?
or is there any signing procedure after packing it?