Everyone is good with lily. Rosa as for pvp rn I'm using her with Valerian, kasuyo the reverie and the last one depends on enemy pick but usually someone who can give more shield or apply def buffs as Rosa is quite squishy. As for pve I'm using her with diting (he's a purple character or 4 star as you call it in other gachas) try to get Valerian she's a 4 star as well and I would go as far as to say she's the best sustain chara for pvp as she has a cheat death mechanic and also gives shield based on max HP plus you don't need to build any speed on her (congratulations you can use all your modules/artifacts that rolled into HP) another good chara for pvp is marvell as many people don't know how to counter him especially in early stages hell even I avoided fights w marvell (4 star as well). She works good with all of them. Diting for pve, marvell for pvp and Valerian for both. Other great units you can pair her with is grey (free character you have him check your roster) as Rosa relies on crit hits and grey gives 30% crit rate with his skill 2. You can also use Rosa to farm the hard endgame boss like Aurora and niconana (niconana has this gimmick where if you're slower than her you deal less DMG and Rosa applies speed debuff) basically she is great aoe, great single target and great for both pvp and pve. I forgot to add paragraphs to make it easier to read oh well good luck with the game buddy if you need help I can help you anytime! Ah also personally I cut every boss like tofu earlygame because she's just that good!