You interpret the limitation correctly. It only applies to IRA-to-IRA rollovers (other than Roth conversions). Distributions from a 401(k) are not subject to the one-rollover-per-year limitation, so both of your distributions from the 401(k) rollovers are disregarded with respect to this limitation.
The distribution from the traditional account in the 401(k) and the distribution from the Roth account in the 401(k) are two separate distributions. The rollover of each is a separate rollover.
Rollovers from a 401(k) should generally be done directly, with each distribution made payable only to the particular IRA that is intended to receive the rollover. Even if such checks are presented to you for conveyance to the IRA custodian, they still constitute a direct rollover. With a direct rollover, there is no 60-day deadline, but it makes no sense to hold onto the checks any longer than is necessary to present the checks to the IRA custodian since you can't do anything else with them. If the rollover is instead done indirectly, the distributions are subject to 20% mandatory tax withholding on the taxable amounts which would complicate completing the rollover of the entire distribution.
Just be extra careful that the distribution from the Roth account in the 401(k) ends up in a Roth IRA and not in a traditional IRA. Mistakenly depositing the Roth money into traditional IRA creates severe complications.
