Q: Replaced water pump and now it makes a loud roaring noise when accelerating

What you are describing sounds like a fan clutch that may be wearing out. A mechanical fan clutch works by helping to control the radiator cooling fan speeds as the engine heats up and cools down. As the motor heats up, the clutch causes the fan to spin faster to help draw more air into the radiator to cool the engine down. As the engine temperature cools down, the fan begins to disengage and spins slower. There are typically two types of fan clutches. The most common is one that is filled with fluid and uses a bi-metallic sensory system similar to that of a thermostat. The second type is an electrically controlled fan that is operated based upon various electrical inputs (i.e. engine oil temperature, coolant temperature, AC system pressures, etc.) that help to control when the fan speeds up or slows down. What you are hearing is likely the fan working harder more often than it should be. I would suggest having an expert from YourMechanic come to your location to take a look at your vehicle to determine what may be causing this.