Spray a 6-quart crock pot with cooking spray.: When you spray the inner pot, you create an easy release so the finished casserole lifts out more cleanly, and it prevents the edges from sticking and tearing. You should notice a faint sheen and a neutral scent from the spray; this step is small but important for presentation. If you skip this, the bottom and sides can cling, making serving messy. Avoid heavy greasing that pools, because it can make the edges overly greasy.
Place cinnamon roll quarters evenly in crock pot.: As you arrange the quartered rolls, aim for an even layer with small spaces between pieces so the custard can soak in. Pressing them flat will change their texture, so leave them slightly puffy to preserve the spiral structure. You should see distinct pieces rather than one compact mass. A common mistake is piling them too high, which can prevent the centers from fully cooking; distribute them in a single, even layer.
In a medium bowl, whisk together eggs, half-and-half, maple syrup, vanilla, cinnamon, and nutmeg.: Whisking melds the flavors and creates a smooth custard base. You will hear a soft whisking sound and see the mixture become homogeneous and slightly frothy on top. This step ensures even seasoning so every bite tastes consistent. Watch out for lumps; if the dairy is cold it can resist smooth mixing, so bring ingredients briefly toward room temperature for ease.
Slowly pour on top of cinnamon rolls.: Pouring slowly allows the custard to sink into the layers instead of simply pooling, saturating the interiors for that tender middle. You should see the liquid seep between the spirals and darken the dough where it soaks in. If you pour too quickly in one spot, it can create uneven soaking, so distribute gently and go around the surface to encourage even coverage.
Sprinkle pecans on top.: Scattering pecans before cooking gives them a chance to toast slightly and adds texture. You will feel a contrast when you press gently, and the nuts will brown a touch during the slow cook. If you add them after cooking instead, you lose the toasting effect, so add now for best crunch. A caution: too many nuts can overwhelm the sweet custard balance.
Spoon one of the containers of icing that came with the cinnamon rolls on top.: Dabbing the included icing across the surface creates pockets that melt into a glossy, sweet finish as the casserole warms. You will see the icing soften and spread, leaving sticky ribbons. This gives the top a bakery style shine and helps attract guests to the table. Avoid over spreading to the edges where it can run into the crock and caramelize too deeply.
Place lid on crock pot and cook on LOW for 2 1/2 to 3 hours. If your crock pot runs hot, check after 3 hours. Cinnamon rolls should be golden brown along the edge and no longer gooey in the middle.: During this slow cook, the appliance will emit a gentle hissing warmth and a heady cinnamon aroma will fill your kitchen. You want the internal texture to transition from doughy to set but tender, signaling doneness when edges are golden and the center is no longer gooey. One common mistake is opening the lid frequently, which causes heat loss and uneven cooking; trust the time window and only check near the end. If your unit runs hot, check after 3 hours to prevent overcooking.
Once done, turn crock pot off and spoon second container of icing on top. Serve warm.: Turning the cooker off lets residual heat melt the top layer gently, and spooning the remaining icing creates a glossy, decadent finish that contrasts with the warm custard beneath. You will see it melt into shallow pools and create a ribboned glaze. Serve warm so the sugar softens and the flavors are most pronounced. A trap to avoid is letting it sit too long; the icing will sink and lose that fresh contrast if left overnight.
Serve warm: Present the casserole while it is still warm so the texture is soft and the icing slightly melty, which makes each forkful comforting and indulgent. Guests will notice the steam and aroma immediately, and the contrast between the golden edges and soft center will be clear. If plated cold, the custard firms and the experience is less glossy, so aim for prompt serving. Reheating gently preserves the texture better than a high blast which can dry edges.