Yes, roll-on deodorant is considered a liquid by the TSA and most international aviation security agencies. Because it contains a gel-like or liquid substance that can be poured or smeared, it must adhere to the "3-1-1" rule: the container must be 3.4 ounces (100ml) or less and must be placed inside a single, quart-sized, clear resealable plastic bag along with your other liquids and gels. This is a common point of confusion for travelers because solid (stick) deodorant does not have to go in the clear bag and has no size restrictions. If you use a spray/aerosol deodorant, that also must go in the clear bag and stay under the 3.4oz limit. If you are looking to save space in your liquids bag, switching to a solid stick deodorant is a highly recommended travel hack, as it can be placed anywhere in your carry-on without counting toward your liquid allowance.