The sphere of residential roofing, much like any other sector, isn't immune to evolution and development. As we venture further into the 21st century, innovative technologies and changing consumer preferences are shaping the future of this industry. With advancements in materials, design and application techniques, numerous emerging trends are ready to redefine residential roofing's landscape.

The first significant trend that's gaining momentum is the use of sustainable and eco-friendly materials. Sustainability has become a key driving force across industries, and roofing is no exception. The shift towards "green" roofs or living roofs – roofs covered with vegetation – is one noteworthy instance. These not only provide superior thermal insulation but also efficiently manage storm water runoff and create habitats for wildlife, aligning roofing with global biodiversity goals.

In contrast to the rustic appeal of green roofs, solar roofs present a sleek, modern alternative. As the urgency to transition to renewable energy sources amplifies, solar roofs are rapidly becoming a mainstream choice. These roofs, fitted with photovoltaic cells, convert sunlight into electricity, thereby reducing reliance on fossil fuels and offsetting energy costs. Moreover, with legislation like the Solar Rights Act, that prevents homeowners associations from banning solar installations, the legal landscape is becoming increasingly favorable for this trend.

Another emerging trend is the use of advanced, synthetic materials. Composite shingles, for instance, are engineered to mimic high-end materials such as slate and wood, but at a fraction of the cost. They offer superior durability, fire-resistance and are significantly lighter, reducing structural stress. The trade-off here is the higher upfront cost compared to traditional roofing materials, but the long-term benefits and reduced maintenance often offset this initial investment.

In tandem with material advancements, roofing design is also evolving. As we see a surge in the popularity of contemporary architectural aesthetics, flat roofs are becoming increasingly common. These roofs offer additional living spaces, can accommodate rooftop gardens or solar panels, and align with minimalist design principles.

In terms of application techniques, drones are revolutionizing how roof inspections and maintenance are conducted. Their ability to capture high-resolution images and access hard-to-reach areas with minimal risk and disruption has revolutionized the traditional, labor-intensive process. By integrating Artificial Intelligence (AI) and machine learning algorithms, these drones can even analyze the data collected and predict future maintenance requirements or potential failures.

While these are exciting developments, it's important to acknowledge the potential challenges. For instance, implementing new technologies will require substantial investment in training and upskilling the existing workforce. Furthermore, the adoption of these technologies must be legislated carefully to ensure ethical use and privacy protection, especially in relation to drone usage.

It's fascinating to speculate how these trends could converge. For instance, could we see a future where AI-integrated drones autonomously monitor and maintain solar roofs? Or perhaps, could composite materials be engineered to integrate photovoltaic properties, creating roofs that are both aesthetically pleasing and energy-efficient?

The residential roofing sector is on the cusp of a transformation, driven by an amalgamation of technological advancements and changing societal norms. It has the potential to not just provide shelter, but also contribute to energy generation, biodiversity, aesthetic appeal and much more. In this dynamic landscape, both challenges and opportunities abound - it's up to us to harness them effectively.