#and then spinning and plying them in particular ways to get stripes or heather or what have you

[milkweedman]

you seem to do a lot of natural dyeing, so i was wondering: is it better to dye wool as roving or after it is spun? im new to spinning but not to dyeing, but ive only ever dyed pre spun wool

it's entirely a matter of preference. dyeing in different preps can give you different options for how the yarn turns out, and some people prefer to dye one way or another because they're worried about felting or because it seems like less of a hassle.

dyeing as yarn: easy to speckle (just tie resist bands). the fiber is in a pretty robust state and many people feel it's less likely to felt. the fiber will be white (or whatever undyed color) as you spin it, which some enjoy and some do not.

dyeing as roving: the fiber is already colored when you spin it (again, for some this is preferable and for others it's not). not super difficult to modify using the rest of your stash as you turn it into yarn (for example you could dye a red roving and then whilst spinning add in occasional bits of blue). you may end up with sections that are darker or lighter and can rearrange them to make different effects if you wish.

dyeing as washed fleece: the fiber is colored before processing and dyeing it. you will end up with darker and lighter sections of fleece which can be neutralized or enhanced. you can easily add in more colors or textures if you have any tools (a pair of hand cards is an absolute spinning game changer and can never be introduced too early, and they're the cheapest fiber tools to start out with).

there are a few other considerations, such as: you will typically get deeper and more vibrant colors when dyeing in the wool vs. in the yarn, but in my experience it's not a huge difference. and i always end up with tangled yarn no matter what i do, but you can't tangle a fleece (and can just pull apart roving to untangle if you manage it). other considerations might be if you plan to throw the dye material in with the fiber--it's a lot easier to pick leaves out of yarn than out of fleece soup. and on very delicate fleeces or fleeces with really beautiful distinct locks i might wait to dye until i've already processed the fleece, since dyeing can jumble fleeces and cause locks to lose their distinctness.

and this is just wrt natural dyeing in a dye pot (as that's what I do and it's what you brought up). if you do acid dyes you can get lots of different effects dyeing one way or another. or you can dye locks one color at one end and a different at the other and get somewhat iridescent yarn because each individual fiber is a different color at each point. you can even dye as top, rolags, or batts. you can paint roving or yarn, each to different effects. you can dye a fleece multiple colors at different points. etc.

TL;DR: there isn't one correct way or one better way, there's only preferences and desired effects. you should experiment with all the different ways to dye as a spinner that interest you and find out what methods you enjoy and what methods are better kept as something to do only because it produces the desired effect.