If you're going to say it to an officemate who returned to work after an illness:
Masaya/Nat
utuw
â kami at nakabal
ík ka na. = (Lit.) We are happy that you are already able to return. = We are glad to see you back.
"Masaya" is an adjective (happy), while "natutuwa" is a verb (are happy).
If you're going to say it to someone who just recovered from illness, regardless of where you are:
Masaya/Natutuwa ako/kami at magal
íng/gumal
íng ka na. = I/We are happy that you are already well/already got well.
"Magaling" is an adjective (that you are well), while "gumaling" is a verb (that you got well).
Your sentence, "Masaya na ikaw ay bumalik", does not say who is happy - is it just you or others too? "Bumalik" is "to return" but it generally means that the action is voluntary on the part of the person who returned. You may even say it, even sarcastically, to someone who just returned from the washroom after an unusually long time. Also, using "bumalik" suggests that the person had the option not to come back, and worse, it may suggest that you were also considering the idea that the person was not coming back and make your greeting sound less sincere. "Nakabalik" is "to have the ability to come back", which is appropriate for someone who was prevented by something beyond his control, like illness, from returning to work.