Having bought a huge amount of washi tape on Amazon, I found the quality in some was lacking. Specifically, the sets that feature 10 or more rolls seem the most likely to resist unrolling, tearing apart as you unroll, or simply remaining stuck.
The washi off Ebay and Etsy seems better, or if you buy in single rolls, you get better quality.
But I found a solution for the stuck washi! Super easy too!
First, look at this sad, stuck washi roll:
It had been cute, with cats and little houses. But it would not unroll without splitting.
Since it was worthless, I took a risk. Putting it on a slightly damp napkin,
I turned the microwave on to 15 seconds. Just enough to create a tiny bit of steam to arise under the roll.
Believe it or not, the tape didn't even get hot to the touch,
but it instantly became usable. This matters if you do splurge on a $10 roll.
Even more fun, if you can't find a sane way to organize your washi,
try my uninspired, super cheap way: a 14" embroidery hoop does the trick fine (I used wood but should have used a metal one).
Lastly, for what it's worth, you can get rolls of washi on Ebay from China for under $1.00 and free ship. Sure, you have to wait a month or so, but a cool treat when they arrive!!!