NIT Rourkela started branch change facility from academic year 2017-2018. For a branch change, your first year CGPA and seat availability in the desired course will be considered. However, to answer you precisely, it is not easy to get a branch change, that too into CSE. Top scorers at NIT Rourkela are able to achieve this feat.
The main obstacle is that students acquire a laid back attitude after getting an admission into an NIT or IIT. Even if you work 1/10th as hard as you did during your JEE preparation, you will get a good CGPA and your chances for a branch change will be high. For this, you will have to work hard instead of blaming the faculty, syllabus or hectic schedule.
It is quite difficult to upgrade to CSE at NIT Rourkela. However, if you work really hard and get lucky enough that the department has vacant seats, you might get into CSE after your first year.