Yes, you can mix rosemary oil with shampoo. Rosemary oil is known for its stimulating and invigorating properties, which can help promote hair growth and improve scalp health. However, it is important to use the oil in moderation, as it can be quite potent. Start by adding a few drops of rosemary oil to your regular shampoo and mix it well before using. This will help enhance the benefits of the oil without overwhelming your scalp or hair.