// returns temperature in degrees C
float getTempC(uint8_t*);
// returns temperature in degrees F
float getTempF(uint8_t*);
// Get temperature for device index (slow)
float getTempCByIndex(uint8_t);
// Get temperature for device index (slow)
float getTempFByIndex(uint8_t);
So, yes all the methods to get the temperature return a float, not an int.
Your buffer will need to be larger, and you'll need to use ftoa(), instead of itoa(). After that, you'll need to put more characters to the display.