Hi Thank you for asking a question. 
As long as it is not painful and there is no ulceration and upon erection, the cracks and roughness go away, then it may not be an issue. The structure of penis is genetically defined, it varies from one individual to another. If it is painful, sore, there is ulceration or it causes a problem during erection or you are having painful, or burning micturition or dysuria then you need to see a doctor, for further evaluation.