I "saw the light" when I began training with rollers. I used a set which had two small rollers in front instead of the single, large roller, the smaller rollers greatly increased pedaling resistance. After 20 or 30 minutes I could keep my balance well enough not to have to hold onto anything, and the first thing I noticed was the sound, the "whir, whir, whir" sound which occurred each time I stepped on a pedal. With a great deal of effort, I was eventually able to pedal with a single, steady "whirrrrrrrrrrrr." This took some weeks.
Using rollers made an unbelievable difference in my pedal stroke, the only equipment I needed was my ears. But another thing rollers helped with was balance and steadiness. Though I had been riding a bike since I was 5, I was not nearly as balanced and steady as I had thought. After my very first session on rollers, as soon as I got on the road I felt a dramatic improvement.
When you begin attempting to pedal in circles, your heart rate immediately picks up, as more muscles are being worked, and more blood is necessary to keep them working. Being able to use all of the muscles in your legs distributes the effort across all of them. At first it is difficult because if you have been pedaling as if you had been climbing stairs, you'll have have strong muscles which are used regularly, and weak muscles which were used very little. Getting those unused muscles to the same level of strength and efficiency as the strong muscles takes time. But once they are strong, you'll notice a big improvement in your riding ability.