I purchased this "roving rose" at the Jay County Spin-in in 2014. There was an ounce of white, an ounce of navy, an ounce of pink, and an ounce of blended colors, in llama, alpaca, and wool. I grabbed it to take with me to the February meeting of the local spinning guild and spun up the already-blended bit.
I tried to blend the solid colors on-the-fly at the meeting, but that was a FAIL. So later that week, I experimented with blending the three colors at home, using all the tools at my disposal.
A blending board is absolutely perfect for blending roving. You just "paint" the board with the fibers, layering colors as you wish.
The result is a fat sausage of a rolag. If the colors seem too separate, you can re-blend them, until they meet with your approval.
I didn't take notes, but I think I re-blended these rolags at least once, if not twice.
I also tried blending on my new drum carder. This worked fine, although it would take some experimenting to get the combination you want.
The resulting batt can be run through again (and again) but from this pic, I think I opted out.
Hand carders may also be used to blend fiber, sort of like a mini-blending board.
I'm not very adept at using the hand carders.
Of these three methods, I like the blending board best. The rolags are fat and tight, and I think you have better control of the outcome.
More fun: spinning the blended fiber! The different methods produced different yarn, depending on how the colors mixed and fed into the wheel.
So now there are four ounces of llama-alpaca-wool, enough for a nice cozy pair of mittens, methinks. I have plenty of hats and scarves but not enough handwear.
But first, I'll take the yarn to the spinning guild for "show and tell".