Healthy root-bound houseplants do typically need to be re-potted into larger pots. The plant has gotten too small for the existing container and needs room to grow.

Roots escaping a pot may indicate poor drainage or lack of water.

Step1
Check the holes in the bottom of the pot (there should be holes for proper drainage). If roots are growing out of the holes, your plant might need to be re-potted. If the plant does not look healthy, or the soil is very dry, this can also indicate that the roots are growing out of the pot trying to find water. Increase your watering schedule or re-pot the plant with gravel pr perlite in the bottom of the pot to improve drainage.
Step2
Look at the top of the plant. Is the foliage overwhelming compared to the pot size? If the foliage excessively spilling over the pot on all sides? This might indicate a healthy root-bound plant that would benefit from being re-potted in a larger pot.
Step3
Moisten the soil and gently pull the plant out of the pot. If there are a lot of thick roots growing in circles at the bottom of the pot, it is most likely root bound.

From my own personal experience, I'd like to share the following:
When watering, I try to avoid watering near the stem, I water at the sides, this will force the roots to grow sideways, and than to grow downwards. Giving you a healthier rootball.

When growing from seed, and after I switch to flower, once I have sexed my babies, and whacked all the males, I will transplant once more. Usually into a 5 gallon growpot. Remember root ball/growpot size is directly related to yeild. A rootbound plant will produce less than a healthy plant.
As a rule of thumb, you want (imo) 1.5 gallons, per foot of plant.
I know alot of peeple will tell you only 1 gallon per foot, but thats wrong.

One last note, doing a transplant during flowering, is DANGEROUS for the novice grower, you do not want to stress the plant. Here are some additional tips for you:

Water the plant slightly just before transplanting, turn the plant sideways, and tap from the bottom, while GENTLY pulling from the stem, and it will just pop out all of a sudden. Place it into your new grow pot, that already has soil in the bottom, after you've done this, just fill in the sides with more soil.

Additionally, when transplanting, use the same exact soil mixture that you've been using. A change in the recipe could cause stress and a disaster would be awaiting you, plants have a tendency to show you when they get stressed by turning hermie on you.
Peace