Many in-house creative teams partner with a wide range of clients in various departments and business units within their companies to develop marketing and communications deliverables. Depending on the particular background of these clients and the depth of their experience and expertise in working with creative teams, their expectations of what their and the in-house agency's contributions to the marketing/communications strategy of a project should be can vary wildly. The opportunity is to identify the disconnect between the client's strategy needs and your in-house agency's strategic capabilities and look for ways to bridge that gap.
Just to clarify, the marketing/communications strategy referred to in this post includes the definition of target audiences, the purpose and objectives of the creative initiative, and the supporting messaging and media platforms. Basically, all project determinations that occur upstream of the actual execution of the tactics, NOT the creative strategy which has its own unique set of practices that are typically creative agency responsibilities that occur during the discovery, research and concepting phases of a project.
Often the marketing/communications strategy required for jobs coming from internal departments whose core function doesn't involve marketing, say HR or IT, is minimal and can be managed by art directors, senior copywriters or creative directors. There are times, though, when a true Tier 1 project from one of those departments walks through the door and requires a level of marketing strategy finesse and expertise that falls outside of the typical scope of a creative group. In these instances, if there were an opportunity to pull in freelance marketing talent, this would be the best route to take.
Another path, if securing external talent isn't an option, is to leverage a member of the Account Management team (assuming your group has one) to assist with the strategy, as many account managers have developed marketing strategy skills over the course of their careers. To lay the groundwork for this option, when hiring future account managers, you may want to take their marketing skills into consideration more than you may have in the past--though be careful not to over-emphasize this aspect of the role or experience, as you may end up hiring an account manager whose intention is to use your team as a stepping stone to a marketing role (which may happen naturally, but to lose someone within 12 months would be unfortunate).
The worst-case scenario would be to inform the client that marketing/communications strategy is needed, your team doesn't possess that capability, and then to steer them to an outside resource, hopefully with the opportunity to bring the execution of the project back to your in-house group once the strategy was completed. (It's a good idea to have some trusted external vendors you could recommend to the client as both a service to your client and also as a means of ensuring the project execution comes back to your team.)
If the volume of work requiring marketing strategy is great enough, establishing a full-time marketing/communications strategist role might be in order. This need most often shows up in smaller companies that lack a robust marketing department and even larger companies who rotate sales staff into marketing roles who then interface with creative services teams, but who have no marketing expertise and therefore require a lot of handholding through the creative process. Even if the marketing strategy hours don't support a full-time role, there are creative professionals you can hire who possess a wide range of skills inclusive of marketing strategy such as copywriters or content managers who can work in multiple functions to ensure full utilization.
Whatever the scenario or need, while including marketing strategists in an in-house agency has in the past been atypical, with social media and even core advertising functions being brought in-house, this is an approach that should be seriously considered if your group is to remain relevant and truly meet your company's creative services and marketing needs.