It is highly unlikely that roaches will enter your house through the sanitary sewer pipes. Every drain fixture has a P-trap that holds water to prevent gases and insects from entering your house. But, you do need to ensure that there is always water in the traps, and they don't dry out. It is more likely that the roach you saw was attracted to the drain to get water. But, the sewer lines are not sealed to the treatment plant. There are plenty of roaches and other insects in the manholes, but, they usually cannot get through the P-traps in your house. Vinegar and baking soda is not needed in the sewer line.
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