If you're not confident in your ability to make it safely past your head, you're not ready to do a front tuck.
Regarding learning how to fall safely, the specifics are skill-dependent. It's a generally good idea to get comfortable rolling in any direction you can think of. Forward, diagonal (like in parkour), sideways, backwards. If the rolls themselves are uncomfortable for you, then that's where you should start. Of particular use are a roll to candlestick and backward roll for anything going backwards. For skills that rotate forwards, it's good to be comfortable doing both a straight forward roll and a PK roll as shown in the video. I don't know your age, but the older you are, the more important rolls are.
As for how to bail from a front tuck:
The short answer is that if you're worried you might need to bail to a roll, you're not ready to work a front tuck.
If you get a halfway decent takeoff and tuck even a little, that should be enough for you to rotate past your head and neck. In other words, if either your strength, your takeoff technique, or your confidence are not at a level where you feel absolutely certain in your ability to at least make it past your head, then you're not ready to work a front tuck.
I don't think a dive roll is useful as a bail from a front tuck. You more or less have to know which one you're going to do before you take off; if you take off like you should for a front tuck, then by the time your feet leave the floor you're already too late to turn it into a dive roll. If you take off for a front tuck and then bail, the best you can realistically hope for is to land flat on your back. On a spring floor or softer, that hurts only slightly less than it sounds like it would; on anything harder than a spring floor, you'll be feeling it for awhile.
The usefulness of a dive roll as a lead up to a front tuck depends on the training context. For young gymnasts (say, under 12) or gymnasts training onto a soft landing surface (preferably an 8-inch mat on a spring floor, or softer), it's a good skill to train in parallel to a front tuck. Building both skills in parallel reinforces strong orientation and control over rotation. However, I don't think a dive roll is necessary as a lead-up to a front tuck, simply because a clean and correct dive roll is at least as hard as a front tuck, if not harder.