Scoundrels and Opertives do not need cover to perform any attacks in their rotation.
Before 3.0 they would use it to make use of explosive probe and snipe(dont know the rep counter names), but due to changes in the game system, snipe no longer requires cover and explosive probe is now sniper/gunslinger only.
Snipe and probe are/were useful because they had 30m range, and range on a melee class is always a benefit.
But now you can snipe without cover.
As for rolling into cover to get somewhere, it can be useful in some situations like pvp.
However this is also a tactic that was used a lot in the early years of the game before operatives got their own roll ability that can be used 2x in a row as gap closer.
You can still use 'roll into cover' when its on cooldown, but you might not always end up where you expected too.
Even as a healer, the ability isn't really a big benefit, operative healers are the most mobile healers.
Placing yourself in cover does not really help you in pvp, you can still be pulled or charged by other classes (unlike snipers who are in cover).
In short; no, you do not need cover as a operative/scoundrel and very few situations will give you a benefit from using it.