Assuming my diseases don't automatically kill everyone I come in contact with:

1. Find someone who is sick with a disease, preferably viral, that I have immunity to, most likely through vaccination. Harvest the infectious agent from them, culture it, and store it as a potential weapon.
2. Invent banking and insurance. Use the diseases developed in 1. to kill or disable anyone who threatens my monopoly. Because Romans lack knowledge of virology, molecular pathology, et al. (see what I did there?) I could do this and remain fairly undetected.
3. Look up the most valuable currently (1 AD) unknown deposits of some resource, and harvest it. Use it to fund my business. This is largely optional, but could help.
4. Find the greatest minds of the time and teach them something relatively simple, like Newtonian physics, ingratiating them to me, and convincing them to join my faction. (We're going into Northern Europe.)
5. Use my massive wealth to fund an army. Use steel for weapons instead of iron. Develop cannons. Attack Rome.