Which one is better for computer science and engineering and why: VNIT Nagpur, NIT Calicut, or NIT Rourkela?

Nobody can answer that fully because no one can attend the three institutes and compare all three of them, in fact, what you can do is ask individuals and pass outs from these and compare their critique and pros. Since, one of my friends studied at VNIT Nagpur, so I might be able to help with the basic details. 

Pros

• The placements are excellent wherein 75% of the department gets placed in the first couple of months of the final year. 
• Eventually, at the end of the academic year, only the students who either need to clear some subjects or have very little CGPA don't get placed, hardly 10–15 students out of 90.
• Around 20 students out of 90 of the second year and 70 students out of 90 of the third year receive summer internships which is a very good amount.
• Experienced teaching faculty and staff with expertise in their respective subjects. 
• Good coding culture, coding club, and monthly internal coding contests to develop your skills.
• You also get a lot of free time especially in CSE in which you can develop your own projects and publish research papers. 

Cons

• The university offers all the required B.Tech courses very well. There are no specialized optional training courses, including last year computer biology. Such courses cannot, however, also be offered in other NITs. 

In April and May, you can find the climate of Nagpur hot. It's fine the rest of the year. You will get used to it and will not mind the consistency of your education. Any other college like VNIT Nagpur will have their own set of pros and cons, it finally depends on you to give priority to the one you like.