The role of ring bearer in weddings is to bring the wedding rings to the altar. Typically, they are between the ages of 4 to 8 years old, and walk before the flower girl does. Two rings are attached to the pillow, usually, they are fake rings, which these accessories can be found at Hispanic/Church Accessories.
What to wear? First rule of thumb here is to make sure they are going to be comfortable. Styles can range from mini tuxs to suits (depending on time of year)
For cooler months, Velvet or Satin suits look great. Usually, darker colors are also worn that compliment the wedding colors.
As for warmer months, white or light colored linen suits.
To add a formal touch, ties and a jacket can be worn.