How do students respond to the "roll call" and how do you pronounce it?

In the US, the most common answer is Here. While Present was also heard in the 1950s and earlier, this has largely disappeared except in smug exaggeration.

There are slight variances in regions across the US with a more significant oh (as in bowl) heard in the Northeast, and less so in the Midwest.

SUPPLEMENT: Calling the roll was used in schools through the late 20th century, and roll call is still used in the military and uniformed services, such as fire and police, and in legislative bodies (as in a roll call vote). Since the 1980s, the phrase taking attendance has become more common, as reflected in this ngram.

As there are a few anecdotal answers here, here's mine (which is more recent - I left Sixth Form a few months ago) - for a state school in the UK:

"Yes/Here Miss/Sir" is the usual reply (obviously the "yes/here" isn't linked to whether it's "Sir" or "Miss").

I've never actually heard anyone speak of calling the register - it was usually referred to (by students and staff alike) as either "taking" or "doing" the register. I never encountered another way of referring to it, so I certainly wouldn't call "taking" dated at all.

If anyone did ever answer with a "here" (as occasionally happened lower down the school) they'd get a raised eyebrow and a long silence until they added a "Sir" or "Miss" to the end.

I've never heard "roll call" used (irl).

Well, I don't know about English schools but in Scotland, more specifically Aberdeen/Aberdeenshire, we say "here." In our school registration is a time to chat and get ready for the day, and because our teacher is quite forgiving, pupils tend to joke about and say "here/here miss," in a funny accent. Registration lasts seven minutes where we read the bulletin (school news). In posher schools in Aberdeen, pupils are required to say "present." All in all, it simply depends on the type of school/ area you are thinking about. Hope this helped!

I can't remember if we said 'present' or 'yes'.

'Roll' is pronounced as in 'bread roll', or 'roll out the barrel'. 'Call' is just as you would say 'call out when you are ready'.