The single biggest rule is that when you roll a traditional IRA into a Roth, you pay taxes on the full amount of the rollover -- traditionals are generally funded with pre-tax money, and Roths always with after-tax money.
Once you have paid all those taxes, you can easily begin withdrawing money from the Roth. Distributions are considered to come first from your (already taxed) contributions or conversions.
It is usually not recommended to roll traditional over to Roth at your stage in life. The taxes will take a major bite out of your retirement money.


