In the addition to the above points,for the FFT points go to the link i have given below
For Understanding of Lp cosine filter and roll of factor visit the given link
https://en.wikipedia.org/wiki/Raised-cosine_filter
For the last one,can you attach the system setup screen shot along with constellation diagrams as i am not able to open the file you have attached.
Hope you got your all answers
Thankyou