Tim Bowen is on a roll with another article on English phrasal verbs.
If a particular event is said to roll around, it means it happens regualrly, as in, 'I see the decorations are up in the shops. It looks like Christmas is definately rolling around again!' In terms of shopping, companies often roll out (release) new products to attract new customers, and for the same reason they may say that they have rolled back (reduced) prices. If they are successful, then hopefully the profits will roll in (arrive in large quantities) for them. When it comes to cosmetics, many products try and attract customers by claiming to roll back the years (reduce the influence of time).
The expression roll over can be used in two ways. It can be used to suggest that somebody is easily pursuaded (though is often used in the negative), as in, 'What do you mean you told him I'd give you £50? Do you think I'd just roll over and give you the money?' It can also be used when talking about money in a lottery that hasn't been won and has thus been added to the next draw's prize fund: 'There were no winners in this week's lottery, so the money has been rolled over to next week.' The prize for the following week is thereafter referred to as a rollover.
If you can't wait or are impatient for something to happen, you might use the phrase roll on! For instance, 'I'm bored of Christmas. Roll on the new year!'