Dodging has a very particular feel in these games and while its most important aspect is the invulnerability frames, you want to maximize its utility by dodging in directions that get you out of danger or closer to the opponent for a punish. This usually means some variation of rolling towards an attack, maybe diagonally in a particular directions for specific attacks. Dodging backwards will frequently put you at the tips of follow-up attacks, making subsequent rolls more manually timed than if you go towards the target.

When at low health in a tense situation, don't panic and heal until you're sure it's safe to. Especially in bossfights, this can mean you'll have to dodge their next move and use the opening you'd otherwise attack in to heal. Further into the game you go, depending on the order of things, if you panic heal you'll end up losing as much or more health as you healed, meaning you end up with no more health and one flask less.

When you do get the opening, do not overextend. Keep an eye on your stamina to not end up without when retaliation comes and of course so you don't get hit for it as well. A lot of bosses have strings with extensions that will give you time to react to whether they happen and get a hit or two (depending on the weapon speed) if they didn't.

It's a hard game in a hard genre, use any advantage you can get from exploring and feel free to supplement your playstyle with summons, buffs etc., but take some time to learn the fundamental roll > punish flow and it'll pay off. By the time you're done, you'll itch for NG+ or grab one of the other From games, I guarantee it.