Watch C-SPAN and you'll see that most votes are taken with electronic voting machines.
Each Member has a credit-card-like card that identifies him and he inserts it into a machine to allow him to vote. There is a certain length of time alloted for voting before the final result is tallied. This gives Members the opportunity to work in their offices instead of hanging out on the floor all day. They can come down just to cast their votes. There is a system of bells and lights throughout the Capitol Building that lets Members know when a vote is being taken so they can get to the floor to cast theirs.
Those not present in the chamber don't vote - BUT they also escape notice as not voting.
A Roll Call vote is called under the rules of parliamentary procedure when one of the parties wants the votes to be publicly recorded. This forces the Members to take a public stand on a piece of legislation.
Both types of votes are public record but the Roll Call Vote call special attention to particular legislation and the votes of individual legislators.
Roll Call votes are usually used for controversial measures so that Members can't hide.
If they don't show up or vote "present," it is public.
Yes or No votes may also place a Member at odds with his constituency back home so RC votes are often used during election years to force unpopular votes that can be used against a candidate in an election.
RC votes are more likely to be covered by the media, especially the media in Congress who report for outlets in the States where Members are from.
Both the Democrats and Republicans use them.
It's great if you can get an opponent to publicly vote against a bill which the public thinks is good. It makes him look bad - even if he has a very good reason for opposing that particualr piece of legislation.