when I straighten my hair, the length of my hair is PERFECTLY straight, but my roots are wavy,any suggestions?

Use smaller sections when straightening your hair that way you get closer to the root. Do not add product before applying heat because it may block the heat from penetrating thru. Never use water based products (gels or creams) afterward it may revert the hair.

I have very curly hair and straighten it as well... What I do is when I blow dry it, I concentrate on the top (roots) and pull it straight with a brush. Then when I straighten it, I take small pieces and use a straightening gel.

take smaller sections near the roots. Use a good flat iron like a CHI, or second best is Babyliss. Chi is way better. Blow dry foreword with a large metal round brush, small sections, and then flat iron, No moisturizers because moisturizers suck up moisture from the air. Use a leave it conditioner designed for thermal protection.

you could try blowdrying your roots (at least that part) straight and then straighten your hair. or maybe if you can use a thinner straightner and reach closer to ur roots...but be careful with that

you can spray static gaurd onto ur brush so when you brush ur hair when ur done straighting it it wont fly away (reallii works). or u can spray some hairspray into ur hands and smooth ur hands down over your hair, but dont use a lot. or juss put hand cram in ur hands and gently pat it into ur hair, again dont use alot.

Shave your head

bump it. take the flat iron and to the ends and very carefully.