can I restore 'ros-latest.list' that I mistook to remove.

edit

can i restore that list?

yes, just run this:

sudo sh -c 'echo "deb http://packages.ros.org/ros/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list'

Or use one of the mirrors (perhaps this one).

or is it no problem for using ros?

For running: no it would not be a problem.

But for installing new packages or updates: yes it would be a problem, as apt would not be able to find the ROS package repositories any longer.