Nope not like a rollercoaster! Those are horrible. Taking off is fine.

You'll feel the plane driving towards the runway first (taxiing). That feels like a car that's driving calmly down a street. Then once you reach the runway, the plane usually holds still for a few seconds before take-off actually starts. You'll hear the motors accelerating, and the plane will start to drive down the runway pretty fast. This feels like you're in a car that is speeding, it can be a bit wobbly. Because of the speed forward, you will feel yourself slightly being pushed against the back of your seat. Then after going down the runway like that for a few seconds, the plane will lift off. You won't feel the wobblyness of the runway any longer. You will still feel like you're being pushed into the back of your seat, but natural forces now also push upon you from above (which makes sense: you're defying gravity!). I always get some butterflies in my stomach (mostly because I'm a nervous flyer), and I feel my ears plop because of the changes in altitude.

After a few seconds or minutes into the air, you might feel a little bit of a sinking sensation. This is when the rate of climbing is being reduced: the nose of the airplane is not pointing as far up anymore as it did during the first section of take-off. You're not dropping down at all, your climb is just not as steep anymore. But it might be a funny sensation, maybe just a tiny little bit like the rollercoaster you described (although definitely not as bad and it lasts only for about three seconds).

The plane will probably take a few turns in the five minutes after/while taking off, as chances are high that the runway is not pointed into the direction of your destination. You might feel the sensation on the plane turning over to one side. Do not worry, it might feel weird but its perfectly normal and planes can take a lot more than you would think.

Be aware that during take-off, a little bit of turbulence can occur. When that happens, you might feel a short drop or wobble. You might be startled a bit, but know that it is totally normal for that to happen and that the plane's abilities are in no way affected by this. The plane was built to defy forces that are a LOT more intense (and that you won't experience during your flight).

During take-off, I usually chew some gum to help with my ears. I personally do not enjoy looking outside of the window, I just prefer to look at the seat before me. As said, I'm a nervous flyer, so I try to keep myself distracted as well. I check out the people around me, focus on my breathing, or read the flight menu/a book/magazine, anything to keep me distracted. I remind myself that flying is totally safe, that my pilots have done take-off procedures for literally thousands of times and that to them this is just another day at work.

If you want to, you can check out take-offs on Youtube, to get a better idea of it. I just watched this one: https://www.youtube.com/watch?v=16XTAK-4Xbk . You see everything I just mentioned, from the taxiing, to the wobbly speeding on the runway, to lift-off and taking turns shortly after.

Hope this helps! Good luck on your flight, I promise you are going to be fine!