Hii Gopal..

First of all congratulations for your success in Jee mains. Coming to your question of comparison between NIT Calicut, NIT Rourkela and NIT Allahabad, my personal suggestion would be NIT Allahabad. 

Since while deciding the college, placement scenario plays an important part. And not only placement but the college culture, the place at which the college is situated and many more factors are the deciding factors for selection of a college. And NIT Allahabad have a great coding culture. Thus if you are willing to choose computer science branch as your major during engineering then your first choice should be off course NIT Allahabad.

And if we considered the placements at the three colleges then in year 2017-18 the package of NIT Allahabad was highest that is more than 7 lakh. After NIT Allahabad the second choice you can have is NIT Calicut and then NIT Rourkela because even the average package at NIT Calicut is more than NIT Rourkela.

Hope it helps..

Best of luck for your future..