See Ritik this has became a common mindset of candidates that they would join some college then after 1 year they would do branch change. Rather than focusing on their curricullum they start to focus on branch change. This affects their results also. 

But as you have asked IIT Kanpur vs IIT Roorkee branch change so i will suggest iit kanpur because they have a slighter flexibility in branch change. Branch change is possible at the end of 2nd, 3rd, 4th semester. Although you have to work very hard in order to score near to 10 cgpa for cse, around 9 for electrical, mechanical.

But i would suggest you to go with what you like rather than going with what people says.