I am making cinnamon rolls with a maple flavoured frosting, however, I am having trouble finding maple extract for the frosting. What can I substitute it with? I have vanilla extract - will it change the taste of the topping too much if I use this?
Well, you are not going to get a maple flavour with anything other than maple extract (or maple sugar or syrup or some similar maple product).
That said, I've substituted rum for maple in some recipes and tend to think of it as a better approximation than vanilla. The caveat of course is the amount; a tablespoon is fine to substitute, an entire cup is going to impart a pretty strong alcohol flavour that you probably don't want.
If you don't have rum or don't think it would work for your recipe, then vanilla extract is probably the next-closest thing. However, it will change the flavour; whether or not that change is "too much" is really a matter of opinion.
Are you looking to retain the maple flavor, or simply for a flavor that will be complimentary to your cinnamon rolls? In many ways, you could use all sorts of extracts, but your cinnamon rolls will be a different flavor. Orange extract might be nice. Almond extract always provides a very delicate flavor (unless you use too much, then it's overpowering) and would also work well. Rum extract would be nice.