Do you know that only 70% of website development projects fail because of poor management? In turn, just 2.5% of businesses finish 100% of their projects as planned.

    As you can see, companies need to use effective web project management techniques to complete the overall business objectives and goals successfully. Defining each member’s role and their responsibilities not only saves your money and time but increases the chance of delivering a high-quality product in a short time.

     As practice shows, programming alone isn't enough to make a website work for you. That's why many stakeholders pay great attention to design and marketing. Respectively, your web development team should fit the project's objectives and consist of specialists with diverse skills and knowledge.

     While some companies provide it's customers with the full circle of specialists they may need for the project, others do not. That's especially true for young and narrowly focused firms.

     So, every custom web development companymay have it's own spectrum of services and the number of web development team members can vary. 
the core web development team roles: Requirement Analyst, Project Manager, Solution Architect, UI/UX Designer, Web Developer, Quality Assurance Engineer. 

More details can be found here https://www.cleveroad.com/blog/web-development-team-structure