There were many longtime libertarians and longtime LP members who supported the invasion of Iraq.
It's not necessarily inconsistent for Root to say "We should declare victory. We achieved our goal. We built a democracy. Let’s get the heck out and the lesson I think I learned is that nation-building is a failure". He probably meant something like the following (from Defending Libervention In Iraq):
We have now achieved our two most important war aims: 1) elimination of any WMD capability or international terrorist infrastructure, and 2) deposing Saddam's regime in favor of a federal democratic constitutional framework designed to protect minorities and fundamental human rights. We would have liked to also successfully transition security responsibility to the new Iraqi government, but Iraq's thirst for civil war has effectively exhausted the reconstruction and stabilization efforts we owed the Iraqis for having liberated them. It is now time to accept our partial victory and let the Iraqi people take responsibility for their own future.
