"He is tired now."
Translation:Tá sé tuirseach anois.
Tá tuirseach orm anois, as was pointed out in the previous comments, isn't correct or idiomatic. You can say either tá tuirse orm (tuirse, like brón or ocras is a noun), or you can say tá mé tuirseach (tuirseach is an adjective, like fluich or déanach).
Usually, the noun form is preferred where you would use a predicative adjective in English to describe a feeling/emotion, so tá brón air for "he is sad" (predicative adjective), but is fear brónach é - "he is a sad man" (attributive adjective). In the case of tuirse/tuirseach*, both forms are in widespread use.
In the case of other types of adjective, there is no problem with using them as predicative adjectives, tá sé fluich, tá sé saibhir, etc.