Can I just barely skim the top of the soil to start a new flower bed, then add top soil and food, then plant? Is the flower rolls that you just roll out on top of the soil and water any good?
Avoid the temptation to skimp on soil preparation. The deeper and better aerated the root zone, the better the plants will grow. Also, avoid thin layers of differing types of soil. If you're going to add topsoil, work it in to the existing soil so there's no distinct difference in soil types. Distinct layers of soil set up barriers to water movement and root penetration.
Flower mats can be a convenient way to seed areas. They are much more expensive than starting from seed then transplanting to the garden.