Yes, funds deposited in a Roth IRA can be withdrawn at any time. If the funds deposited represent Roth IRA contributions then those amounts can be withdrawn tax-free and penalty free. If an amount in excess of the contributions is withdrawn then that amount would be subject to income taxes if it is not a qualified distribution (and a 10% penalty if before age 59 1/2.
Conversion amounts can also be withdrawn tax-free. However, if conversion amounts are withdrawn prior to 5 years and before age 59 1/2 then there is a 10% penalty.