The TC-4 shield won’t roast coffee for you, but this homeroasters.org project will help you gather data from up to four thermocouples. From the related code repository:
Probably best to think of the TC4 as programmable interface hardware for multiple thermocouple sensors.
…support(s) both standalone operation using an LCD display and/or data logger operation if the TC4 is attached via USB cable to a PC.
Bourbon is a straightforward monitoring and logging application. When used as part of a standalone system it displays elapsed time, BT, ET, and BT-RoR on a 2-line LCD. Since Bourbon creates and sends a continuous data stream over the USB serial interface, realtime graphic display of roast history as well as CSV format data logging can be done if you connect the TC4 to your computer.
Here is forum member Rama’s implementation:
I roast my own coffee and would love to add better (more obsessive) temperature measurement to the mix.
You can get a bare PCB here, as well as a bill of materials for the necessary components.