Is it normal to have 3 roots instead of 2 roots in teeth?

Depends on tooth: It depends on the tooth. Most upper molars have 3 roots and lower molars ususally have 2 roots. Sometimes there will be extra roots on a tooth. They will usually show up on an x- ray, but not always.

Perfectly normal: The number of roots can vary in a tooth depending in genetics.

It happens: Lower molars and upper first premolars usually have two roots but may have three roots on occasion. There are individual variances in the 'normal' number of roots teeth have.