Can I use a large jug, such as a Carlo Rosse bottle, with an added airlock as a carboy for fermentation? Are there any issues with this or things I should make sure to do?
Sure. At the end of the day, a carboy is just a container. They're not rated for pressure, they're not thermally-hardened, they're … just a container. Glass is glass is glass. (Plastics come in various types; oxygen permeability and surface roughness are particular concerns). You might have "trouble" finding the right size airlock for the opening, but airlocks are overrated anyways. ;)