Actually you have your cold tolerences reversed. The Filifera (Cal. Fan Palm) is more cold tolerant. That said, the trunk of a Robusta is a much deeper maroon than that of a filifera. It is most noticeable at the base of the fronds (Filifera will have some green mixed in). There is also a chance that it is a hybrid between the two which is supposed to be more cold tolerant than either of the others. I could not tell you how to tell the hybrid apart visually.

Pretend your sago is variegated, wx,I would just remove the dead stuff if you want to cut,leave all the green tissue on the palm,think of it this way,every leaf you cut off now will be at least one leaf less this year. If you leave your palms uncovered now and it rains, there is a good chance you will see spear pull regardless of if it hits mid to low 20s or just 30F I live quite a ways south of you and we have already seen many 60s 70s and near 80F and I am not uncovering mine until we have a week of 70+ weahter forecast,Washys really don't start growing until it gets above 70F anyway ESPECIALY coming out of winter,I would hate to see you lose your Washys.etc after doing such an awesome job of protecting them this winter! I don't know of anyone growing Washys as far north as you are-Cold soil,air and moisture are almost surly a death sentence esp for washys....Watchout for next weekend!

Robustas are leaf hardy to the low 20's, which you already know. At 15º, much depends on the size of the palm and the type of protection. I would mark the emerging spear and some other petiole (as a reference) and watch the next two weeks for growth. Washies would normally have grown a little already in z8.

Welcome Chad, Very nice Robusta!! Your Robusta will do fine inside in a sunny location. Just make sure you have it planted in a very well draining soil and don't overwater it. Once a month during the winter is plenty. Your Robusta will grow very fast. You can control the size somewhat by keeping it in a smaller pot, but eventually it will become rootbound and need potted up. A 7 gallon pot should do what you want to do for the next two years. The yellowing on older fronds is normal. Wait until the chance of frost is over and put it in a partial sun location. Morning sun is best. After a few weeks move it to full sun so it can enjoy the sunshine. Craig