What would be my function as Taliyah?

She's pretty much purely focused around roaming, it's like an Aurelion Sol situation. You can do fine in lane, but overall you're entire focus is getting other lanes ahead.

Most of what I see built is some combination of Obviously take appropriate boot choices.

She's not a common choice anymore as there are stronger roaming champions who have 4 damaging abilities rather than 3.

Ap midlaner but im not sure how well she does in the meta, you dont see her much any more which is sad

Be ready to lose lane but make sure to roam before you do, look for flanks with ults or cut off the adc from teamfights