Yes, HubDuino already has support for the MAX31855 thermocouple board.
Great!
Can he do multiple 31855's on one NodeMCU?
What did you end up doing? I have a very similar set of requirements for a temperature sensor in the attic.
Ah, yes, you’ve got me.
I followed all the good and helpful advice above, bought all the components, and then… life got in the way.
Also, as a relatively quick solution that met some of my needs, I bought a SwitchBot temperature sensor and hub.
This has the benefit of working out of the box, and storing records, graphing them nicely. Ticks lot of boxes, if I’m honest.
It’s a shame it doesn’t integrate with Hubitat, but maybe one day somebody will write some nice code for it.
It’s running on batteries at present, and when they die, I’ll probably do a trip into the loft space and hard wire it in.
I’d still like to get the above project working, for other applications. When I get a moment, I’ll work on that. Just need to build the extension first. 
