Yeah, roseleare is slow to start but it helps to keep at 70-75 degree for th first few days. The. You can bring it down to normal room temp for the long duration of aging for 12+ months.
***i had really pour results in a 5 gallon batch that was fermented clean and then roseleare in secondary. 18 months and it still was not very sour.
For your barrel project, do you have a couple brewers that will ferment primary with funk? If so you are good. Your results using those yeast/bacteria cakes will be better then if you just make a couple small starters, and certainly better then if you pitch packs of roseleare directly into the barrel (after primary).
The best case scenario would be if ALL brewers in the barrel project used a sour blend for primary. Wyeast, white labs, and East Coast Yeast.
Our first barrel turned out amazing after 15 months with 3/4 of it fermented clean in primary though!