Help with 1-Wire to I2C translate
As you said, the DS18B20 uses One-Wire interface. I2C is a Two-Wire interface. Pratically, you can't use the Arduino to translate that, BUT I found the  DS28E17, a module that could translate the the 2 methods of communication. It should work but I havent tested it.



The DS28E17 is a 1-Wire slave to I2C master bridge device that interfaces directly to I2C slaves at standard (100kHz max) or fast (400kHz max). Data transfers serially by means of the 1-Wire® protocol, which requires only a single data lead and a ground return. Every DS28E17 is guaranteed to have a unique 64-bit ROM registration number that serves as a node address in the 1-Wire network. Multiple DS28E17 devices can coexist with other devices in the 1-Wire network and be accessed individually without affecting other devices. The DS28E17 allows using complex I2C devices such as display controllers, ADCs, DACs, I2C sensors, etc. in a 1-Wire environment. Each self-timed DS28E17 provides 1-Wire access for a single I2C interface.

Hope I helped you.